Redistricting and Congressional Control Following the 2012 Election

November 28, 2012

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On Election Day, Republicans maintained control of the House of Representatives. While two Congressional races remain undecided as of November 20, it appears that Democrats may have picked up about eight seats during the 2012 election,[1] falling well short of the 25 seats Democrats needed to take back control of the House.

Before the election, the Brennan Center estimated that redistricting would allow Republicans to maintain long-term control of 11 more seats in the House than they would have under the previous district lines.[2] Now that the election is complete, it is worth re-examining the influence of redistricting on the results of the 2012 election. This brief assesses how the new district lines affected the partisan balance of power in the House. The report is the prologue to more extensive analyses, which will examine other aspects of redistricting, including the fairness of the process and its effect on minority representation, among others.

Based on our initial analysis of the 2012 election, several important trends emerge:

  • Redistricting may have changed which party won the election in at least 26 House districts. Because of redistricting, it is likely that the GOP won about six more seats overall in 2012 than they would have under the old district lines.
  • Where Republicans controlled redistricting, the GOP likely won 11 more seats than they would have under the old district lines, including five seats previously held by Democrats. Democrats also used redistricting to their advantage, but Republicans redrew the lines for four times as many districts as Democrats.
  • Republican gains during redistricting were largely because vulnerable Republican incumbents received safer districts. Redistricting safeguarded at least eight Republican incumbents who would have otherwise lost re-election in 2012. Six of these eight were freshmen elected in 2010.
  • Of the 79 sitting members of Congress who will depart before the start of the 113th Congress, over one-half — about 40 — will not be coming back partly because of redistricting. Many of the departing members of Congress did not run for re-election or lost in a primary election, but of the 26 incumbents who lost on Election Day, 19 of those casualties were redistricting-related.

The 2012 election data in this report are based on election returns reported by The New York Times, current as of November 17.[3] These election returns are not certified and are therefore subject to change. North Carolina's 7th district remains undecided. The Democratic candidate is currently leading and we include this district in our analysis, provisionally counting it as a Democratic victory. A second district, Louisiana's 3rd, will feature a run-off election in December; both candidates in the run-off are Republicans, so the seat is guaranteed to stay in Republican hands.[4]

I. Where Redistricting May Have Changed Which Party Won The Election

This section assesses whether the change in the partisan composition of each district following redistricting may have impacted which party won the district in 2012. For example, consider a district where the Democratic candidate in 2012 won with 52 percent of the vote, while the Republican candidate received 48 percent. If the territory in the newly drawn district historically gave Republican candidates about six percent less of the vote than the old district, it is likely that the Republican candidate would have won under the old district lines. Therefore, our analysis would estimate that redistricting likely changed which party won the election in 2012 from Republican to Democratic.

Historical voting patterns in the old district and the new are measured using the data and methods described in Appendix A of Redistricting and Congressional Control: A First Look.[5] The analysis is conservative in identifying districts where redistricting may have changed the election outcome. In some districts, redistricting made the 2012 election uncompetitive. As such, our analysis suggests that the election result would not have been any different under the old district lines, even though a competitive election in the old district may have led to a different result.

Of course, it is not easy to determine with certainty what the outcome of the 2012 election would have been under the old district lines. Without having the candidates on the ballot in the old district as well as the new district, there is no way to know precisely what percentage of the vote each candidate would have received this election in the old district. Still, the analysis below provides a reasonable approximation of where redistricting may have changed which party won the election in 2012.

Based on our analysis, there are at least 26 districts where redistricting may have changed which party won the 2012 election:

  • Nine seats likely flipped from Republican to Democratic control because of redistricting:
    • AZ-01: Ann Kirkpatrick (D) defeated Jonathan Paton (R). This seat was formerly held by Rep. Paul Gosar (R).
    • CA-07: Ami Bera (D) defeated Rep. Dan Lungren (R).
    • CA-26: Julia Brownley (D) defeated Tony Strickland (R). This seat was formerly held by Rep. Elton Gallegly (R).
    • CA-52: Scott Peters (D) defeated Rep. Brian Bilbray (R).
    • FL-22: Lois Frankel (D) defeated Adam Hasner (R). This seat was formerly held by Rep. Allen West (R).
    • IL-08: Tammy Duckworth (D) defeated Rep. Joe Walsh (R).
    • IL-10: Brad Schneider (D) defeated Rep. Robert Dold (R).
    • IL-17: Cheri Bustos (D) defeated Rep. Bobby Schilling (R).
    • MD-06: John Delaney (D) defeated Rep. Roscoe Bartlett (R).
  • Eight seats likely flipped from Democratic to Republican control because of redistricting:
    • IN-02: Jackie Walorski (R) defeated Brendan Mullen (D). This seat was formerly held by Rep. Joe Donnelly (D).
    • IA-03: Rep. Tom Latham (R) defeated Rep. Leonard Boswell (D).
    • KY-06: Andy Barr (R) defeated Rep. Ben Chandler (D).
    • NY-27: Chris Collins (R) defeated Rep. Kathy Hochul (D).
    • PA-12: Keith Rothfus (R) defeated Rep. Mark Critz (D).
    • NC-08: Richard Hudson (R) defeated Rep. Larry Kissell (D).
    • NC-11: Mark Meadows (R) defeated Hayden Rogers (D). This seat was formerly held by Rep. Heath Shuler (D).
    • NC-13: George Holding (R) defeated Charles Malone (D). This seat was formerly held by Rep. Brad Miller (D).
  • Republicans kept control of eight seats they would likely have lost without redistricting:
    • FL-10: Rep. Daniel Webster (R) defeated Val Demings (D).
    • MI-01: Rep. Dan Benishek (R) defeated Gary McDowell (D).
    • MI-11: Kerry Bentivolio (R) defeated Syed Taj (D). This seat was formerly held by Rep. Thad McCotter (R).
    • MN-06: Rep. Michelle Bachmann (R) defeated Jim Graves (D).
    • NC-02: Rep. Renee Ellmers (R) defeated Steve Wilkins (D).
    • OH-06: Rep. Bill Johnson (R) defeated Charlie Wilson (D).
    • PA-11: Rep. Lou Barletta (R) defeated Gene Stilp (D).
    • TX-27: Rep. Blake Farenthold (R) defeated Rose Harrison (D).
  • Democrats kept control of one seat they would likely have lost without redistricting:
    • AZ-02: Rep. Ron Barber (D) defeated Martha McSally (R).  

The list above does not include incumbents like Judy Biggert (IL-08), Nan Hayworth (NY-18), and Ann Marie Buerkle (NY-24), who lost, in part, because of unfavorable changes to their districts, but who may have also likely lost in their old districts, based on their respective margins of defeat in 2012.[6] This list also does not include the four incumbent Democrats in California who lost re-election to a Democratic opponent due to redistricting and to the state's new top-two primary election system.

Based just on the seats that flipped party control, Democrats likely ended up gaining one net seat in the House because of redistricting. Before the election, the Brennan Center had accurately estimated that Democrats would gain one seat in the House by that measure.

But where Republicans really took advantage of redistricting was in shoring up some of their most vulnerable members. Accounting for incumbents who were protected by redistricting, we estimate that Republicans likely won six more seats overall in the 2012 election than they would have won under the old district lines. Before the election, the Brennan Center estimated that Republicans would maintain long-term control of 11 more districts than they would have under the old district lines. Redistricting helped Republicans slightly less in 2012 than our longer-term estimate would suggest. In part, this is because Democratic incumbents like John Barrow (GA-12), Mike McIntyre (NC-07), and Jim Matheson (UT-04) won re-election despite unfavorable changes to their districts during redistricting.

Yet the estimated six seat gain for Republicans also does not include districts where redistricting made re-election less competitive for the incumbent, allowing the incumbent to win comfortably even though a more competitive contest in the old district might have yielded a different result. For example, freshman Republican Reps. Cory Gardner (CO-04), Randy Hultgren (IL-14), Todd Young (IN-09), Steve Chabot (OH-01), and Patrick Meehan (PA-07) all received significantly safer districts. According to The Cook Political Report, their contests were all considered competitive during the Republican wave in 2010, yet none of their contests were considered competitive in 2012.[7] But even though the Democratic candidates were not competitive in these districts, the 2012 election results suggest that the Democrat in each race would have come within five points of defeating the incumbent under the old district lines.

II. The Outcomes of Partisan Redistricting

Six different types of authorities controlled the redistricting process: Republican legislature and governor; Democratic legislature and governor; an independent commission; a politician commission; a state or federal court; or a state legislature and governor with split control between Republicans and Democrats.[8] This section focuses on the outcomes of Republican-controlled and Democratic-controlled redistricting. The Brennan Center will examine the results of redistricting for the other four actors in greater detail in our forthcoming analysis in the spring.

Republican legislators and governors drew district lines for 173 of the 435 seats in Congress.[9] Where Republican legislators controlled redistricting, Republicans likely won 11 more seats than they would have under the old district lines. Five of these 11 were seats that flipped party control due to redistricting; six were Republican seats saved by redistricting. In states where Republicans controlled redistricting, Republican candidates for the House won roughly 53 percent of the vote and 72 percent of the seats. But even under the old district lines, that disparity would have persisted, as Republicans still would have likely won about 65 percent of the seats.

Democratic legislators and governors redistricted 44 seats, just one-quarter the number of seats as Republicans.[10] But they still used redistricting to their advantage. Where they controlled redistricting, Democrats won three more seats than they would have under the old district lines, and Republicans lost five more seats. In the six states where Democrats controlled redistricting, Democratic candidates for the House won about 56 percent of the vote and 71 percent of the seats. However, that disparity would have persisted even before redistricting, as Democrats would have likely won 61 percent of the seats under the old district lines.

III. Congressional Turnover and Redistricting

Following the election, 79 sitting incumbents will depart the House. (There will be 84 freshmen in the 113th Congress; five freshmen were elected to vacant seats.) About 40 of the 79 departing incumbents may not be coming back at least partly because of redistricting:

  • 39 incumbents did not run for re-election to the House, and at least 10 of those departures may have had something to do with redistricting. Five saw their districts splintered or eliminated during redistricting: Reps. Steve Austria (R-OH), David Dreier (R-CA), Jerry Lewis (R-CA), Lynn Woolsey (D-CA), and Bob Turner (R-NY). Five others saw their district significantly altered to their disadvantage during redistricting: Reps. Joe Donnelly (D-IN), Elton Gallegly (R-CA), Tim Johnson (R-IL), Brad Miller (D-NC), and Heath Shuler (D-NC).
  • 13 incumbents lost in primary elections, and 10 of them lost at least partly because of redistricting. Eight incumbents were paired with an incumbent from their own party during redistricting and lost the primary election: Reps. Ben Quayle (R-AZ), Steve Rothman (D-NJ), Don Manzullo (R-IL), Dennis Kucinich (D-OH), Hansen Clarke (D-MI), Russ Carnahan (D-MO), Jason Altmire (D-PA), and Sandy Adams (R-FL). Meanwhile, Rep. Tim Holden (D-PA) and Rep. Cliff Stearns (R-FL) became more vulnerable to primary challenges when they were drawn into new territory during redistricting.
  • 26 incumbents lost on Election Day, and 19 were significantly weakened by redistricting. Fifteen of these incumbents lost to an opponent from the opposing party and were more likely to win re-election in their old district: Reps. Dan Lungren (R-CA), Brian Bilbray (R-CA), Leonard Boswell (D-IA), Joe Walsh (R-IL), Robert Dold (R-IL), Bobby Schilling (R-IL), Judy Biggert (R-IL), Ben Chandler (D-KY), Roscoe Bartlett (R-MD), Larry Kissell (D-NC), Nan Hayworth (R-NY), Ann Marie Buerkle (R-NY), Kathy Hochul (D-NY), Betty Sutton (D-OH), and Mark Critz (D-PA). In California, four Democratic members lost in the general election to a Democratic opponent, thanks both to redistricting and the state's new top-two primary system: Reps. Howard Berman, Joe Baca, Laura Richardson, and Pete Stark.
  • In December, one final incumbent will lose because of redistricting. In Louisiana, two incumbents — Reps. Charles Boustany (R) and Jeff Landry (R) — will face each other in a run-off election. The two were paired together during redistricting.

Notably, of the 40 members whose departure may have been at least partly the result of redistricting, 20 were Democrats and 20 were Republicans.                     


[1] One undecided race is North Carolina's 7th district. Democrats lead in this race; we provisionally count it as a Democratic victory. A second race, in Louisiana's 3rd district, will feature a run-off in December between two Republican candidates in December. House Map, The New York Times (Nov. 17, 2012), http://elections.nytimes.com/2012/results/house.

As of November 20, The New York Times results map did not reflect the fact that the Republican candidate in Florida's 18th district has conceded to the Democratic candidate. Sean Sullivan, Florida Rep. Allen West Concedes, The Fix Blog (Nov. 20, 2012, 7:35 AM), http://www.washingtonpost.com/blogs/the-fix/wp/2012/11/20/florida-rep-allen-west-concedes/.

[2] Sundeep Iyer & Keesha Gaskins, Redistricting and Congressional Control: A First Look, Brennan Center for Justice, Oct. 25, 2012, http://www.brennancenter.org/content/resource/redistricting_and_congressional_control_a_first_look/.

[3] House Map, supra note 1.

[4] See supra note 1.

[5] See supra note 2.

[6] Biggert lost by 16.2 percent; Buerkle lost by 4.6 percent; Hayworth lost by 3.4 percent. House Map, supra note 1. All of these margins are larger than the partisan shifts in their districts due to redistricting.

[7] 2012 House Race Ratings for November 5, 2012, The Cook Political Report (Nov. 5, 2012), http://cookpolitical.com/house/charts/race-ratings/5105; 2010 Competitive House Race Chart, The Cook Political Report (Nov. 1, 2010), http://cookpolitical.com/archive/chart/house/race-ratings/2010-11-01_12-12-36.

[8] See Appendix B, Redistricting and Congressional Control, supra note 2.

[9] See Appendix B, Redistricting and Congressional Control, supra note 2.

[10] See Appendix B, Redistricting and Congressional Control, supra note 2.