The following diary is an alternate history. There are two ground rules:
1) As with the 1920 Census, the 2000 reapportionment did not occur, nor did the one in 2010.
2) No districts were altered despite population disparities. In other words, the districts from the 2000 congressional elections were kept.
In this diary, I will be going state-by-state through how this alters what happened in reality and finally looking at the composition of the House of Representatives to see how things changed. One important thing to note is that competitive districts often lead to more money for challengers. Therefore, I counted any race where an incumbent beat an underfunded challenger by 4% or less as an incumbent defeat and one where they beat them by 5% or 6% as a potential defeat. After each map, I will give a rating of how many times it caused the other side to win. For example, a map which on the old lines caused two more Democrats to win, each for three terms, would receive an R+6. Republicans gained 6 terms of Republican congressmembers through their mapmaking skills.
Category 1: States Where Results Barely Budged
There are many states where redistricting makes little to no difference. They comprise a few groups.
1) 1-District States: These cannot be gerrymandered. They are Alaska, Montana, North Dakota, South Dakota, Wyoming, Delaware, and Vermont
2) Districts That Don’t Change: In a few states, the district lines are historic and move only as much as necessary. These are small states. They are Idaho, Maine, New Hampshire, Rhode Island, West Virginia, Nebraska, Kansas, and New Mexico.
3) Medium States that Don’t Budge Much: These states are similar to category 2, but they have changed the lines somewhat in the recent past even when it wasn’t necessary. Some of these states also were forced to add or subtract a district in the last 20 years due to reapportionment, and I will go slightly more in depth with them in a bit. The states that have kept the same number of districts and same general shape since 1992 are Oregon, Arkansas, and Kentucky. That is not to say they aren’t gerrymandered, by any means. Massachusetts, Connecticut, Oklahoma, Mississippi, and South Carolina make up the second category here. The first four lost districts, while South Carolina gained one.
Massachusetts’s lost district, like all its other districts, was a Democratic one, John Olver’s. Since it has only been gone one term, the Massachusetts map gets a score of R+0.5 (as adding a district is only half of a “flip” compared to winning a seat the other party holds). Connecticut, which lost Jim Maloney’s blue district centered around Waterbury, Danbury, and Meriden, gets a score of R+4 (Chris Shays would have lost in 2006 instead of 2008 under the old lines. Mississippi was forced to eliminate Blue Dog Ronnie Shows in 2002. His old district was the second bluest in the state but still would have voted for Bush twice, McCain, and then Romney. Considering these facts, I am going to assume that Shows loses in 2010 along with fellow Democrat Gene Taylor. That gives the Mississippi map a score of R+1. Oklahoma shed former Democrat, but current Republican Wes Watkins, who held a district in the southeast quadrant of the state. That map gets a D+3. South Carolina of course added Republican Tom Rice in 2012, so their map is an R+0.5.
Category 2: Interesting, But No Real Changes
Here is Minnesota’s old map. 
. In the 2000s, there were many close races in Minnesota house districts. Five of the eight districts held races that were considered tossups, probably the highest percentage of any state with a double-digit number of electoral votes. And the map did change the partisanship of the districts. In 2000, John Kline’s district moved right while Mark Kennedy’s moved left; in 2010 the opposite happened, with Erik Paulsen’s moving rightward as well. Despite all this, using the 1990s map leads to no changes in the final outcomes. And here is Washington’s. 
It merits a D+0.5 because of the new 10th district, added in 2012. However, nothing else changes on the older map. Amazingly, Dave Reichert, between 2004 and 2012, wins by four, two, four, four, and eight (or possibly fewer, since his 2012 challenger was weak) points. Yet he always wins. Of course, on the new map his district is redder.
Iowa is a similar case; it also had many close races over the past six cycles. The old map is radically different from the current one. 
However, besides the fact that Boswell still has his own seat instead of getting merged with Latham, nothing much changes here. This means Iowa is an R+0.5 map. Of note, however, is that Steve King is much more vulnerable on the old map. He wins by 8 in 2006 and 7 in 2008 against no-name challengers and by only 2 in 2012 against Christie Vilsack.
Category 3: Moderate Drama
Now, things really start to get interesting. In 2002, Alabama’s Democrats still controlled the state legislature, and they drew what they thought was a great gerrymander. And really, it was quite nice, weakening the Blue Dog 3rd and keeping the 5th safe for Bud Cramer, a strong play for a 3-4 map in a red state. It fell apart when Joe Turnham lost to Mike Rogers in the 3rd, but where it really turns out the map helped was in the 2nd district. You see, this was the old map. 
On this map, Jay Love beats Bobby Bright 51-48 in 2008 instead of narrowly losing to him. So I’d say this is still a pretty well done gerrymander. It gets a score of D+1.
Indiana was also drawn by the Democrats in 2002. 
It worked out pretty well, but the old map actually would have led to the same results in the competitive 8th and 9th districts in the southern part of the state. Where it really mattered was in the 2nd. In 2006, Joe Donnelly wins, old map or new, 52-48 on the old. However, he would have lost in 2010 instead of narrowly hanging on, a 49-46 defeat to be exact. This may have caused him to not run for Senate (or it might have encouraged him to, one never knows), but either way that means Indiana’s map is also a D+1.
Missouri’s big story of the past decade was Ike Skelton’s defeat and the confinement of the Democratic party to essentially Kansas City, St. Louis and its inner suburbs, St Joseph, and Columbia. But let’s examine the old map. 
This 3rd district is much redder than the one Russ Carnahan inherited from Dick Gephardt, which means Missouri would have seen a Congressman Martin (Ed, to be specific) in 2010, at which point he may well have taken over Todd Akin’s seat when his own was eliminated, depriving Republicans of rising star Ann Wagner. This map scores at a D+0.5 when you add in the fact that the 3rd was eliminated, but I put it in this category due to the drama.
Nevada is here because most of the excitement is purely from the population growth. The 1st district was Vegas, the 2nd was everything else, which means it grew explosively between 1990 and 2010. That causes Dean Heller to lose to Jill Derby in 2006, 49-47. She holds the seat in 2008 and then loses it (I would presume, although it’s possible she holds on) in 2010. That gives it an R+2 from the lines and a D+1 from reapportionment, for an R+1 total.
Wisconsin is the last state in this category and it’s all due to the eliminated 5th district, which combined blue Milwaukee County with red Wauke$ha. When Gerry Kleczka retires in 2004 from this seat, the southern of the two blue ones in the east seen here, 
, who knows what happens? I’m calling the district a tossup all the way from 2004 to the present day, although it probably swings with the tides in 2006, 2008, and 2010.
I’m not going to go in-depth on Utah, but on the 1990s map Jim Matheson wins by double digits even in 2012 and doesn’t retire in 2014. There is also no 4th district, so it’s a D+0.5.
Category 4: Major Changes in 1 Seat
Colorado is a mix of reapportionment and redistricting affecting the results. The old map is here. 
The 6th, the lightest red on the map, is the one we want to examine; other districts switched hands but not due to the mapmakers. This 6th was carved in two in 2002, Tom Tancredo’s safely Republican 6th and Bob Beauprez’s swingy 7th, later to be Ed Perlmutter’s starting in 2006. If the 6th were kept whole (and very overpopulated), Tom Tancredo would be in major trouble as a bombthrower in a purple seat. In 2004, he wins only 52-47, and in 2006 51-47 against a no-name. In my calculations, that means with DCCC investment and recruitment, which would surely happen in a purple seat, Tancredo loses, followed by Democrats giving the seat back in 2010. The map’s score thus ends up at R+3.
The 2000 Michigan redistricting was pretty brutal for Democrats. The old map was this one. 
I’m going to go through all the interesting districts here since there are quite a few. The 1st (North), 7th (South Central), and 9th (the only red one near Detroit) all flipped back and forth due to the candidates and the year, not the maps. The 1990s map doesn’t change that. The 8th (Lansing) is still kept by Mike Rogers all decade, but he won 52-46 in 2006 and 53-44 in 2008, both against underfunded candidates, on this old map, so it’s conceivable he may have lost one or both of those races.
The other districts are more complicated because of how much they changed due to Republican gerrymandering. Lynn Rivers (Ann Arbor) and John Dingell (Southeast) were merged into one blue district, while Thad McCotter got to take a pretty safely Republican seat in the Detroit suburbs with the shreds of both seats. That gives the Republicans 6 seats right there. David Bonoir held a swing seat in the east of the state (it’s the one that says 94 inside it on this map), but he chose to run for governor in 2002. I don’t know for sure if this was due to redistricting or not; I’m playing this conservative so I’m going to assume he was going to run anyway. Regardless, Republican Candice Miller, won by such a ridiculous margin, 59-40 under the old lines, that he might have lost either way and she certainly would have won even on those older lines, so I’m considering this a seat the GOP would have won regardless. Michigan’s old 5th district, a C-shaped one containing Bay City and Saginaw, was safe for labor Democrat Jim Barcia, but his district was completely eliminated in redistricting. This gave Republicans another 3 seats, 0.5 times 6. Dale Kildee was the lucky beneficiary; his old district stretched from Flint into the southeast, taking in rapidly suburbanizing northern Oakland and Macomb Counties. It was a pale blue in 2002 and by 2010 may have shifted to pure purple. Regardless, he loses 53-45 (if not more) to Some Dude John Kuipec in 2010 and may have been completely blown out by a better challenger, Virg Bernero-style. The 2012 election would then be a tossup. In sum, this map is R+9. I have to give the Republicans credit here.
New Jersey is similar to Michigan. All the action is in a couple districts. 
This is the old map. Thanks to strong Republican incumbency, the swingy 2nd is safely Republican on either the 1990s or 2000s map. In fact, only the 6th, 7th, and 12th are interesting in the slightest (and of course on this map Steve Rothman continues to serve in Congress, so this map starts off at R+0.5). Let’s start with the 6th. The old, redder 6th district causes Frank Pallone to only win by 4 in 2010 against an okay challenger, but Republicans never win it. The 3rd was interesting in reality, but in this counterfactual nothing changes from that reality, so in my mind it’s pretty boring. Mike Ferguson was a big winner on the 2000s map. On the older one (his district is the lighter red one in the northern half of the state), he wins 50-48, 52-47, and 51-48. And that’s all before the Democratic wave years, in which his seat is one of the top pickup opportunities. I have him losing to Linda Stender 54-43 on these lines. It’s unclear how she does in 2010, so I have that one a tossup, but regardless Democrats hold the seat again in 2012 with either Stender or Upendra Chivukula. The 12th is somewhat the opposite (it’s pale blue here). Rush Holt, fresh off a less than 1% victory in 2000, cements himself pretty well in the seat, but 2010 is bad enough that it doesn’t matter and he goes down 51-48 to Scott Sipprelle, who loses in 2012 after a somewhat fluky, Buerkle-esque victory. In total, this map merits an R+3.
Tennessee is the one state you’d think we’d have gotten to by now. If you’re wondering why, it’s due to strong Democratic gerrymandering in 2002. 
On this map, the highly elongated 4th took in enough of Appalachia and the southern tier of the state to stay red alongside some Blue Dog neighbors. Democrats changed that, helping Lincoln Davis to victory, but here we’re assuming that doesn’t happen. In that case, you can say hello to Congresswoman Janice Bowling. If you’ve never heard of her, you aren’t the only one. She would make Tennessee the only state with three female Republican members of Congress in this alternate scenario and would have beaten Davis by a hair, 49-49. This also would mean no Scott DesJarlais. Tennessee is a D+4, the best score so far for Democrats.
Category 5: Gerrymandering Galore
Arizona is similar to Nevada; lots of demographic changes and some very overpopulated districts assuming the old map is kept. 
I’m going to go year-by-year here.
2002: Rick Renzi succeeds Bob Stump in the northwestern district (a mix of the current Kirkpatrick and Franks districts), 54-42. Due to lack of reapportionment, Trent Franks and Raul Grijalva don’t get to Congress.
2006: Harry Mitchell beats JD Hayworth 50-46 and Gabby Giffords picks up the 8th 55-42.
2008: Rick Renzi leaves Congress to face trial for bribery. However, his district is far redder than the one in reality. Ann Kirkpatrick wins the Democratic nomination, but my guess is she faces someone stronger than Sydney Hay. If it’s Hay, Kirkpatrick wins 50-45, and it’s a Tossup against an actual elected official. John Shadegg and Harry Mitchell both hold onto their seats, 52-43 and 53-44 respectively.
2010: If Kirkpatrick wins in 2008, she loses to Paul Gosar 55-38 here, making her initial victory a real fluke. Ben Quayle wins an open seat 50-42, Dave Schweikert beats Mitchell 53-43, and Gabby Giffords holds on 50-47.
2012: Ron Barber wins the special election to succeed Giffords and then loses to Martha McSally 51-49. Quayle and Schweikert aren’t merged, meaning no Sinema, and the new 4th district which Gosar jumped to in reality doesn’t open up.
In short, this map is a disaster for Democrats. It merits a D+3, since the real maps were better for Team Blue than this one.
Georgia was a Democratic gerrymander (and a bit of a dummymander) in the 1990s, so that is the map we are sticking with here. 
For some background, Sanford Bishop (blue in the south) and Bob Barr (light red in the west) were coming off competitive re-elections, and Saxby Chambliss (south central) left office to run for Senate.
2002: Firstly, reapportionment never happens. This is terrible news for Democrats, as David Scott’s safe seat isn’t created, nor is the new eastern seat that is held by Republican Max Burns for one term but is then held by John Barrow until today. That’s D+5 off the bat. Secondly, due to the lack of redistricting, Phil Gingrey is never endangered and even worse for Democrats, Jim Marshall doesn’t win to replace Chambliss. Instead, Calder Clay takes the seat 54-46. Honestly, it’s kind of fitting; his name is almost as awesome as Chambliss’s.
2004, 2006, and 2008: Nothing. Democrats hold only 3 of the 11 seats.
2010: Democrats drop to 2, with Sanford Bishop losing to Mike Keown 53-46 in a redder seat.
2012: Keown wins, although it’s probably pretty close.
So this map is D+11. Just brutal.
Louisiana, like Minnesota, had a lot of close races last decade, and here many of them go the opposite way. This is the map we are using. 
You can see there is one Black district, two Cajun districts, two northern districts, and two other districts. In 2000, nothing was that close; Republicans held the red seats, Democrats won the Black seat, and Chris John won the southwestern Blue Dog seat.
2002: 6 districts weren’t close, but the open 5th was. In real life, Democrat Rodney Alexander, now a Republican, narrowly beat Republican Lee Fletcher thanks to Democratic gerrymandering. Here Fletcher wins 52-48, but the impact is relatively small since Alexander switched in 2004 anyways. To finish up, Fletcher suffered a tragic death from cancer in his 40s and thus wouldn’t still be in Congress today.
2004: This is where Democrats fall apart on the old map. Charles Boustany wins John’s seat 55-45, not too different from reality. In actuality, Charlie Melancon won an upset victory to take the 3rd district in the southeast of the state, but on the older map, where more of the suburban areas are included, Melancon loses 51-49 to Billy Tauzin III, dropping Democrats down to 1 seat out of 7.
2008: A special election leads to a brief partial term for Democrat Don Cazayoux in the Baton Rouge district, but I’m ignoring that. More interestingly, Democrats move up to 2 seats rather than falling to 0. How? Bill Jefferson manages to win despite the $10,000 in his freezer, but only 49-47. Paul Carmouche also wins the open 4th 48-48 over John Fleming, although I’m certain it would be a one-term rental.
2010: Jefferson resigns due to conviction and Carmouche loses.
2012: Tauzin’s seat isn’t eliminated.
Score: D+4.5. Another Southern map that was a lot worse for Democrats in its 1990s iteration.
Maryland’s districts have been ugly for 6 terms now thanks to the Democrats. The map here, 
wasn’t that nice either but it looked better.
We like to think of Connie Morella (well, those of us who think of her at all) as somewhat invincible, the kind of Republican who could dominate Susan Collins style in a blue area. Looking back, that’s untrue. In 2000, she won only 52-46. On these older, redder lines…
2002: Helen Bentley wins 60-40 instead of Dutch Ruppersburger winning Bob Ehrlich’s seat. Morella hangs on 53-47 (see what I mean about her not being invincible?)
2004: Faced with more bluing in Montgomery County and more straight-ticket voting in a presidential year, there’s a good chance Morella loses, but it’s not for sure.
2006: Morella clearly loses here; stronger blue-district Republicans like Jim Leach and Nancy Johnson did.
2008: Frank Kratovil wins 54-44.
2010: Kratovil loses 50-46 to Andy Harris.
2012: Roscoe Bartlett wins, 50-46 or better. My guess is better because John Delaney wouldn’t have run in the older iteration of the seat. But on the old lines Bartlett beat Delaney by only four.
Score: D+8.5
Virginia has had a very effective Republican gerrymander for a while now. You can see their attempt at an 8-3 here, which was successful for quite some time. 
In 2000, Republican Ed Schrock was coming off a 52-48 win in the light red Virginia Beach district, and Norm Sisisky had just won his last election in the larger of the two very blue districts nearby. He would die in 2001 and be replaced with Republican Randy Forbes. Here’s how everything else played out, starting in 2002:
2004: Schrock retired after a sex scandal, leading to Thelma Drake holding the seat 53-47.
2006: In this older version of the seat, Drake lost to Phil Kellam, 50-50. In NoVa, Tom Davis narrowly held on 51-48.
2008: Davis retired, leaving the seat to Gerry Connolly. Randy Forbes was held to a 55-45 victory. Virgil Goode beat Tom Perriello 51-49.
2010: Scott Rigell beat Kellam 51-44 (or more narrowly). Morgan Griffith beat Rick Boucher 51-46, and Gerry Connolly held on 54-45.
2012: Rigell narrowly won, 52-48 against Paul Hirschbiel. Randy Forbes won 51-49, meaning he would have lost with a better challenger.
Score: R+1 (VA2 2006, VA5 2008, VA4 2012)
North Carolina: This state has seen incredible gerrymandering by both sides in the past decade. 
The 1990s map, while far from tame, was a moderate gerrymander.
2002: Brad Miller’s district isn’t created.
2004: Nothing of note.
2006: Robin Hayes holds on 53-47, while Heath Shuler beats Charles Taylor 54-46.
2008: Larry Kissell beats Hayes 53-47.
2010: Shuler wins 54-46 again, Kissell wins 50-46, Mike McIntyre hangs on 53-47, and Renee Ellmers beats Bob Etheridge 52-47.
2012: Democrats pick up 2 seats here rather than getting slaughtered. Larry Kissell wins 54-46 despite weak fundraising, as does Mike McIntyre. Heath Shuler opts to stay in office and hangs on. (If he’d retired, Mark Meadows would win only 51-49 over Hayden Rogers, which means Rogers might have won with more party investment) Finally, under the old lines both Renee Ellmers and Robert Pittenger win 49-48, so I’d predict both would lose with better or at least better-funded opposition, particularly Ellmers who faced a nobody.
Score: R+6
Category 6: The Big States
We have all the big states left: Illinois, California, Ohio, Texas, Florida, Pennsylvania, and New York.
This is Ohio’s map from the 1990s. 
The 1990s Ohio map featured five safely Democratic seats. Marcy Kaptur had Toledo, Dennis Kucinich and Stephanie Tubbs Jones split Cleveland, Tom Sawyer had Akron, and Huck Finn had Youngstown (actually, it was Jim Traficant). Six more seats were swingy. Sherrod Brown had a gerrymandered seat in NE Ohio, as did Steve LaTourette. Pat Tiberi had a Columbus seat, Tony Hall had Dayton, Ted Strickland had some Blue Dog rural areas, and Steve Chabot had Cincinnati. The remaining eight seats were safely Republican, six rural and two suburban, one in Columbus and one in Cincinnati. In 2000, not much was competitive. Chabot and Tiberi both won by nine, but that was the closest of any race in that cycle in the state. Going chronologically, once again…
2002: Tony Hall retired after over two decades in Congress. Like David Bonoir in Michigan, I can’t prove it was due to redistricting, so I’m going to be conservative and assume it wasn’t. Mike Turner won the open seat 54-46 (on the bluer old map), so I’m certainly not sure he’d have beaten Hall had Hall not retired, but as I said I’m assuming Hall retires anyway. Ted Strickland, vulnerable in a far less blue seat on this map (you can see how it goes far from traditionally Democratic Southeast Ohio into the Cincinnati exurbs), wins 53-47. Tom Sawyer isn’t eliminated.
2004: Nothing of note, despite the size of the state.
2006: The Democratic wave causes many Republican seats to become vulnerable. First and foremost, Bob Ney’s scandal causes Democrat Zack Space to easily pick up the seat. Republicans Jean Schmidt (53-47), Mike Turner (54-46 vs. a weak opponent and Steve LaTourette (52-45 vs. a weak opponent as well) win by moderate margins. Democrats do pick up two seats they would have picked up in 2008 anyways. Steve Chabot goes down to John Cranley, 52-48, while Mary Jo Kilroy beats Deborah Pryce 51-49.
2008: John Boccieri wins an open seat 55-45 in Canton, and LaTourette wins 53-44. Kilroy and Cranley let the wave carry them to victory.
2010: Here it gets a bit crazy. Three Democratic incumbents (Boccieri, Kilroy, and Charlie Wilson, who replaced Strickland) lose by double digits in this brutal year for the party. Dennis Kucinich wins 52-45 in his blue seat. Bob Gibbs defeats Zack Space 50-45. Finally, in a real shocker, Tom Ganley beats Betty Sutton (Sherrod Brown’s replacement) 50-50 in the oddly shaped outer Cleveland area seat. Also, John Cranley hangs on 51-47 (I’m assuming he’s equally as strong as Steve Dreihaus), one of the few Democrats to do so in a competitive seat.
2012: Ganley, who faced rape allegations and barely won in 2010, clearly loses, since the seat isn’t eliminated. Pat Tiberi wins only 54-46, as does Steve Stivers, both against no-name opposition. Gibbs wins 55-45, underperforming. Finally, David Joyce replaces LaTourette and wins 49-44.
Score: R+4.5
Florida:
Florida has gained a lot of seats in recent decades. Back in 1990 they only had 23. Here is the north: 
. And here is the south: 
In 2000, two Republicans narrowly won: Ric Keller in the Orlando area and the late Clay Shaw along the coast in South Florida. Proceeding from there,
2002: Firstly, the new districts (Diaz-Balart, then Rivera, then Garcia in South Florida and Feeney, then Kosmas, then Adams, then Mica on the Space Coast) are not created. We see four moderately close races. Winning with 54% of the vote are Clay Shaw, Katherine Harris, and Corinne Brown. The last two dramatically underperform, especially Brown. Karen Thurman wins 51-43 rather than losing her seat; she was a redistricting casualty in North Florida, representing Gainesville and coastal areas.
2004: Thurman wins, but it’s impossible to know by how much. Harris wins 55-45.
2006: Ric Keller holds on 50-49, but other Republicans are less lucky. Mark Foley resigns and his seat is won by Democrats 54-43. Ron Klein thrashes Clay Shaw, 58-40. Finally, Christine Jennings defeats Vern Buchanan in the open Sarasota seat, 51-49.
2008: Alan Grayson beats Ric Keller 55-45, and Tom Rooney takes back Foley’s seat easily.
2010: There are multiple question marks here, but let’s start with the knowns. What we know for sure is Dan Webster beats Alan Grayson by double digits. Ron Klein holds off Allen West 53-47. Steve Southerland takes the North Florida Blue Dog seat 50-45. Beyond that, I’m assuming Jennings loses, as she narrowly won in a wave year. Kathy Castor wins 53-47 at best, but the GOP may have challenged her better in the redder seat that didn’t include St Petersburg. My guess is she still wins, but it’s a Tossup. Finally I’d guess Republicans strongly challenge Karen Thurman and they just might beat her, especially since the coastal areas have been growing with Republican retirees.
2012: If Thurman wins in 2010, she does fine here. If she loses to Richard Nugent, it’s unknown whether he wins or loses himself. Southerland wins 52-48. Tom Rooney vs. Patrick Murphy would also be a Tossup in a purple seat. Finally, Val Demings thrashes Dan Webster 56-44. Reapportionment denies Florida Alan Grayson Part Two and one of Rooney and Murphy.
Score: R+4
Texas: This is by far the biggest question mark, and my numbers here may be off. Texas Republicans redrew the map in 2004 and intentionally drew Blue Dog Democrats into areas that are Republican downballot instead of swingy downballot, so using the presidential numbers here may screw things up far more than it does in other states, and it’s all I have access to. Considering pretty much no other Southern Democrats lost in 2004 in the House, it seems unlikely multiple ones did in Texas, but it’s possible it’d have happened anyway. 
Here’s the statewide view.
This is the Dallas area.
And this is Houston and Austin.
In 2000, Chet Edwards won 55-45, but nothing was even within single digits.
2002: Lack of reapportionment means no Jeb Hensarling in the Dallas area or John Carter in Williamson County. Three races were competitive. Charlie Stenholm’s West Texas district went for him only 53-46, as did Chet Edwards’s neighboring district. Finally, Henry Bonilla, a Republican from the vast Mexican Border area, won 51-48.
2004: This is the year I’m unsure about. According to my adjustments, a few of the Texas Democrats drawn into new districts lose anyway. In the east, Louie Gohmert beats Max Sandlin 58-42, and Ted Poe beats Jim Turner 56-43. Ralph Hall switches parties, leading to the demise of all East Texas rural Democrats except Nick Lampson, who wins easily in his Beaumont-Galveston seat. The last Democrat to lose is Charlie Stenholm, 54-44 to Mike Conaway. Chet Edwards holds on 53-45, while Tom DeLay wins only 51-45. Martin Frost remains in office, meaning no Kenny Marchant.
2006: Not much is competitive here. Henry Bonilla wins 51-49, unlike his loss in reality.
2008: In the old DeLay district from the 1990s, Nick Lampson beats Pete Olson 49-48. But in this alternate reality, Lampson is already in office in his old seat. So I’d say it’s a Tossup if another Democrat beats Olson or whether Lampson had unique strength. It’s also unknown if Henry Bonilla could win in a year with higher Hispanic turnout than in 2006. The final unknown is whether Pete Sessions loses. Against a Some Dude, he won 51-47 so I’m going to say yes he does.
2010: There are fewer unknowns here. A cycle after winning by 11, Chet Edwards loses by 21. Quico Canseco wins 54-40 if a Democrat is in the seat, otherwise Bonilla still has it. Blake Farenthold narrowly beats Solomon Ortiz. Sessions’s seat is won back by the GOP. Lampson is the only question mark; is he strong enough to have held on in 2010 in the old district?
2012: Quico Canseco wins 49-47, defeating Pete Gallego. Filemon Vela takes back Farenthold’s seat. Pete Sessions or his successor loses again. In reality in the district, Sessions won by 2 against a nobody. Finally, four congressmen don’t make it to office: Roger Williams, Blake Farenthold (his new seat doesn’t exist and Vela beats him), Steve Stockman, and Mark Veasey. Lampson stays in office, defeating Randy Weber.
Score: R+4.5
New York: Here is a map of Downstate, followed by Upstate. 
At the start of the decade, Democrats held every New York City seat except Staten Island, one suburban seat (Nita Lowey), two Long Island seats (Steve Israel, picked up in 2000, and Carolyn McCarthy), Maurice Hinchey’s Ithaca to Woodstock seat, Mike McNulty’s Albany seat, Louise Slaughter’s Rochester seat, and John LaFalce, who held a seat from Rochester to Niagara. 2000 saw, as said earlier, Israel’s pickup of Rick Lazio’s seat, but no races including that one were within single digits.
2002 saw two seats eliminated, one from each party. John LaFalce lost his, and moderate Republican Ben Gilman retired after over three decades from his Rockland County-Middletown seat. In terms of competitive races, there was only one. Tim Bishop made Republican Felix Grucci one of the only incumbents to lose his seat in 2002, 51-48 on the east end of Long Island.
2004: Republicans Jack Quinn in Buffalo and Amo Houghton in the Southern Tier both retired. Quinn’s seat was taken by a Democrat, while Houghton’s was held by Randy Kuhl 51-41.
2006: Here’s where things get interesting, as the wave hit even the moderate Republicans in historically GOP Upstate New York. To begin with, I’m assuming Gilman (sitting in a D+5 or so seat) either is defeated or retires due to age. In terms of Democratic pickups, Mike Arcuri takes the Utica seat 52-47, John Hall takes the Poughkeepsie seat 55-45, Kirsten Gillibrand takes the eastern upstate seat 54-46, and Dan Maffei beats Jim Walsh in this bluer Syracuse seat, 52-48. Three other vulnerable Republicans hold their seat. Firstly, Randy Kuhl holds on 52-48. Secondly, Tom Reynolds keeps his western New York seat 54-46. Finally, Peter King on Long Island only wins by six, which against a legitimate challenger is probably a tossup in my opinion.
2008: Mike McMahon easily takes the Staten Island seat, and shortly after the election Scott Murphy holds Gillibrand’s seat in a special election. Eric Massa beats Kuhl 51-49, and finally, amazingly Mike Arcuri loses in 2008 of all years to Richard Hanna, 50-50.
2010: This is the year where everything went to hell for Democrats due to their holding so many purple to light blue seats upstate. Of course, Hanna had already won in 2008 so there was less for Democrats to lose. Eric Massa resigned and the GOP won his seat, Mike McMahon went down 51-48 to Michael Grimm, Chris Gibson beat Scott Murphy 54-46, and…well…that was it. On the older map, this isn’t terribly bad. Losing 3 seats in a 29 seat state in a wave isn’t horrible, although it’s certainly not good. If one adds in Bob Turner’s special election victory that makes four, but that was clearly 2011. Narrow Democratic holds are: Tim Bishop 51-49, Carolyn McCarthy 53-47, Maurice Hinchey 53-47 (in a vote sink!), Bill Owens 48-46, Dan Maffei 52-48, and John Hall 51-49. The latter two both lost in reality, but not here.
2012: Well, firstly Hinchey and Turner were not eliminated. Most likely, Turner loses. He’s no moderate and was basically holding a half-term rental. Tim Bishop wins 53-47, Grimm wins 52-47, Owens 51-47, and Reed 54-46. John Hall keeps fighting instead of Sean Patrick Maloney.
Score: R+7.5
Illinois: Here is Chicagoland 
. Here is the whole state. 
In 2002, Illinois adopted a kind of incumbent protection map, which helped preserve Republican suburban seats but also Lane Evans and Jerry Costello downstate. David Phelps, a Blue Dog from the southeast of the state, was cut. 2000 had seen three competitive races. Mark Kirk narrowly held the Lake County seat, 51-49 in his initial election. Tim Johnson won 53-47 in east central Illinois, and Lane Evans won 55-45 in the Rock Island area.
2002: Obviously, Phelps survives. Also of note, well…nothing. At all.
2004: The Illinois suburbs begin to turn a bit on the GOP. Jerry Weller is held to a 53-47 margin in his LaSalle County to Joliet district, and Henry Hyde wins only 55-45 in his DuPage one. But the big shocker, and in fact the biggest non-wave shocker of the decade besides PA-17 in 2002 perhaps, is Phil Crane losing to Melissa Bean in the red 8th district, directly west of Kirk’s seat. Also, at this point I think Phelps is vulnerable the right Republican. There aren’t really any Midwestern Blue Dogs in red seats as a comparison. IN-8 is the only really similar one, as well as MN-7, but Peterson is super popular and the seat is less red. I’d say his re-election in 2004 is a tossup. If he wins, he survives until 2010.
2006: A few very close races here. The less close ones are Phil Hare succeeding Evans 55-45 and Melissa Bean winning re-election 51-44. Mark Kirk again survives 51-49. Peter Roskam narrowly holds Hyde’s seat, 50-50 against Tammy Duckworth. But the big one is Jerry Weller losing 50-50 to John Pavich.
2008: Kirk again hangs on by the skin of his teeth, 50-50. Judy Biggert is challenged for the first time, winning 53-44, and in a special election Bill Foster picks up Speaker Hastert’s old seat 52-48.
2010: Adam Kinzinger beats Pavich 52-48, Randy Hultgren beats Foster 52-44, and Bobby Schilling crushes Hare 55-41. Those are the pickups. Interestingly, Melissa Bean narrowly beats Joe Walsh with 48% of the vote, and Dan Seals succeeds Mark Kirk 51-49.
2012: Roskam, not vote sinked like in reality, wins 54-46. Bean and Seals both triumph, although who knows by how much. Adam Kinzinger wins 54-46 at best, the margin may have been closer but I don’t think he loses. Bill Foster defeats Judy Biggert 51-49, and Bobby Schilling stays in office 52-48, proving his popularity in a pretty blue, non-suburban seat. Finally, Don Manzullo isn’t eliminated, and Rodney Davis comes nowhere close to losing.
Score: R+1.5
Pennsylvania: This state has been home to one of the most brutal Republican gerrymanders, although the one last decade collapsed a bit. Here is the 1990s map, both SEPA and the rest of the state. 
2000 saw three members of Congress face close calls. Don Sherwood won 53-47 in his Northeast/Scranton seat, Pat Toomey won 53-47 in the Lehigh Valley, and Joe Hoeffel won 53-46 in the Philly suburbs. Republicans responded by trying to make every member safe, but they overextended themselves. On the old map, here’s what happens…
2002: In reality, two seats needed to be dropped, and both were Democrats: Bob Borski in Philadelphia and Frank Mascara in Southwestern Pennsylvania. I figure both survive until the next redistricting on the old map; Mascara’s seat got redder considering Altmire and Critz survived 2010 (Altmire in a redder seat) I’d say Mascara holds on too. In other races, Paul Kanjorski survives 51-47 in a redder seat, and Joe Hoeffel wins only 50-49. Bill Coyne retired in 2002 after his district was redrawn into a red seat for Tim Murphy, but that’s discarded here. Finally, we have George Gekas instead of Jim Gerlach, because Tim Holden keeps his seat instead of moving to Gekas’s and defeating him, and Gerlach inherited the redrawn old Holden seat.
2004: Nothing is competitive.
2006: Democrats pick up three seats. Jason Altmire beats Melissa Hart 53-47 in the Northern Pittsburgh area seat. Chris Carney crushes Don Sherwood 59-41. And Joe Sestak beats Curt Weldon 56-44 in Delaware County. Other Republicans face close calls. Phil English wins 52-44 in NW PA and Mike Fitzpatrick hangs on by less than 1% in Bucks County, defeating Patrick Murphy. Finally, John Murtha, not given a gerrymandered seat like in real life, wins only 52-48 and I’d say has a 50-50 chance of losing against a better challenger.
2008: Kathy Dahlkemper knocks off English, 53-47, but Paul Kanjorski and John Murtha both lose, leading to Congressmen Barletta and Russell.
2010: Republicans take back two more seats. Mike Kelly beats Dahlkemper 54-46, while Pat Meehan wins Sestak’s seat 55-44. Jason Altmire hangs on 52-48, and Chris Carney keeps his seat against Tom Marino 51-49 thanks to Scranton.
2012: Altmire isn’t merged with the old Murtha seat, so he wins. Carney continues to keep his seat, too. Four races are close. Mike Kelly wins by four and Lou Barletta are six, both against Some Dudes, so I’d say those are tossups. Another tossup is Mascara’s old seat. Battling lung cancer that would kill him in about a year, I’d guess he retires and the purple seat would be a real battleground. Finally, Charlie Dent wins only 53-47.
Score: R+9.5
California: The conventional wisdom about the California map is that it was an incumbent protection map which looked good at the time but was far too tame for a state that would move quickly leftward during the decade. There is some truth to that, but it is far from absolute. 2000 had seen many close races featuring Democratic incumbents, that much is true. Here are the 1990s court-drawn maps. 
2000 saw 7 close races. In NorCal, Ellen Tauscher won 53-44, the last time a Bay Area district would be truly competitive. Mike Honda also easily picked up Tom Campbell’s old Bay Area seat. Cal Dooley won 52-46 in a district that looks a lot like David Valadao’s current district. Lois Capps won 53-44 in a district nearly identical to her current one. Adam Schiff also won 53-44 in an L.A. County seat that would soon be Safely Democratic. Jane Harman won 48-47 in a less liberal version of Henry Waxman’s current seat. Susan Davis won 50-46 in San Diego. Finally, a lone Republican won a close race, Steve Horn by 1% in L.A. County; his district would shortly be dismantled. But let’s assume this map held.
2002: The first thing to note is that Devin Nunes got California’s new seat in 2002. So we remove him from the equation. Beyond this, there are three close races. Lois Capps wins 50-47 against a weak challenger, which by my formula means she actually loses. You can see that she did actually need to be protected by the Democratic gerrymander. Another Democrat who needed to be protected was Gary Condit, or rather his seat. After retiring due to a major scandal involving an intern he slept with who turned up dead, Condit attempted to leave his seat to Dennis Cardoza. It was successful in his bluer real district, but in the 1990s iteration, Republican Dick Monteith triumphs 52-43. It’s not even close. Finally, my guess is Steve Horn narrowly wins again, but it’s anybody’s guess if that’s the case or not.
2004: Monteith wins again, perhaps by single digits and perhaps by double. Another Central Valley Democrat, Cal Dooley, retires. Republicans pick up his seat on the old map, with Roy Ashburn winning 51-49. This probably gets interesting later in the decade when he becomes the latest in a line of gay Republicans to be outed in the Larry Craig mold. Lois Capps’s district would again be a Tossup, as would Steve Horn’s. Finally, David Dreier loses! The incumbent protection gerrymander really protect him throughout the 2000s, but he loses to Cynthia Matthews 49-48 on the old map, where his district is entirely in Los Angeles County.
2006: Roy Ashburn faces a tough re-election; it’s another tossup. If a Republican holds the Capps seat after the 2004 election, they lose it here. John Doolittle holds on up north 49-46, while Jerry McNerney beats Richard Pombo 56-44. Finally, Steve Horn retires or loses in the Democratic wave. Monteith and Matthews hold on.
2008: Instead of the net change of zero on the old map, Democrats pick up four to six seats here. Republicans hanging on by a thread include Ken Calvert 51-49 in Riverside, Brian Bilbray 52-44 in North County San Diego, and Buck McKeon 54-46 (or closer) in Northern LA County. There are two more tossups: Monteith might lose here due to the wave in an R+4 seat that got bluer over the decade, and if Roy Ashburn wins in 2006 he might lose here in a district that ended up about D+2 by 2008. Democrats pick up Doolittle’s open seat, with Charlie Brown beating Tom McClintock 51-49. Bill Durston also narrowly beats Dan Lungren by less than a percent. Finally, in SoCal Elton Gallegly and Gary Miller both lose their seats in major surprises, assuming they face legitimate challengers.
2010: The GOP snapback gives them anywhere from a 2 to 6 seat pickup. Certainly Republicans retake CA-20 if they lost it in the first place; Vidak beat Jim Costa despite his incumbency advantage in this old district. Charlie Brown is a clear goner, only having won because of McClintock’s weakness. Capps’s district is once again vulnerable. At this point it’s California’s Bloody Eighth, with Capps or her successor narrowly losing against a strong challenger. Gary Miller’s old seat is a tossup, as is Elton Gallegly’s. Dick Monteith or Tom Berryhill hold the Condit/Cardoza district. In better news for Democrats, Cynthia Matthews and Bill Durston hold their seats, and Jerry McNerney wins 51-44. However, in the special election to succeed Jane Harman, Craig Huey beats Janice Hahn 51-49.
2012: Huey loses his one-term rental seat. Jerry McNerney and Ken Calvert both survive by single digits. Democrats win back the Bloody 23rd. Raul Ruiz beats Mary Bono Mack 53-47. Finally Brian Bilbray holds off Scott Peters 55-45 in a much redder seat.
Score: D+5. In the end, the map did help Democrats some, especially in the Central Valley.
Here is what the House breakdown looks like.
2002: 230R-205D
2004: 231R-204D (GOP +1)
2006: 241.5D-193.5R (Dem+37.5)
2008: 261.5D-173.5R (Dem+20)
2010: 237.5R-197.5R (GOP+64)
2012: 224R-211D (Dem+13.5)
In the end, it’s not that different, but Democrats have between 4 and 12 more seats every cycle from 2006 onward than they did in reality.
Finally, here are the scores for each state, so we can see in which states the 2000/2010 redistrictings had the most impact.
GA: D+11
PA: R+9.5
MI: R+9
MD: D+8.5
NY: R+7.5
NC: R+6
CA: D+5
TX/OH: R+4.5
LA:D+4.5
TN:D+4
FL/CT:R+4
CO/NJ: R+3
OK/AZ: D+3