Analysis: Texas gave House GOP biggest gerrymandering bump

AUSTIN, Texas (AP) — Voting districts drawn by Texas’ Republican-controlled Legislature helped the party win nearly four more U.S. House seats than it otherwise would have in the last election, which was more than any other state, an Associated Press analysis of the results of federal and state legislative races found.

Gerrymandering, in which the party in power alters the electoral maps to favor itself, helps explain why the GOP continues to be so dominant in Texas despite the rapid growth of the state’s Hispanic population, which tends to back Democrats. The findings also underscore years of federal court rulings that have found Texas’ electoral maps to be unconstitutional and discriminatory.

The AP scrutinized all 435 U.S. House races in November using an “efficiency gap” statistical method designed to calculate partisan advantage. It found that the GOP may have won as many as 22 additional congressional seats than expected based on the average vote share in congressional districts across the country.

The AP’s analysis was based on an “efficiency gap” formula developed by University of Chicago law professor Nick Stephanopoulos and Eric McGhee, a researcher at the nonpartisan Public Policy Institute of California. Their mathematical model was cited last fall as “corroborative evidence” by a federal appeals court panel that struck down Wisconsin’s Assembly districts as an intentional partisan gerrymander in violation of Democratic voters’ rights to representation. The U.S. Supreme Court has agreed to hear an appeal.

Stephanopoulos and McGhee computed efficiency gaps for four decades of congressional and state House races starting in 1972, concluding the pro-Republican maps enacted after the 2010 Census resulted in “the most extreme gerrymanders in modern history.”

The efficiency gap formula compares the statewide average share of the vote a party receives in each district with the statewide percentage of seats it wins, taking into account a common political expectation: For each 1 percentage point gain in its statewide vote share, a party normally increases its seat share by 2 percentage points.

The AP used their method to calculate efficiency gaps for all states that held partisan House or Assembly elections for all of their districts in 2016. It showed that Texas provided the GOP with 3.7 extra House seats. The next closest pro-GOP states were Michigan, North Carolina and New York, which each gave the party at least two House seats that they otherwise would not have gotten.

Texas’ high number of extra Republican House seats was partly the result of its sheer size. The state’s 36 congressional districts are second only to the 53 in California, where a nonpartisan commission draws electoral maps.

Texas’ 10.3 percent efficiency gap favoring Republicans was the 10th highest among the more than two dozen large states that comprise the vast majority of congressional seats, just behind the 10.7 percent Democratic advantage in Maryland.

Overall, Republicans won 25 U.S. House seats from Texas in November, including eight in which they ran unopposed. Democrats won 11 seats, including two in which they ran unopposed.

Rice University political science professor Mark Jones said Texas’ Legislature has been effective at drawing congressional districts that Republicans win comfortably but often not overwhelmingly, while disproportionately packing liberal voters into districts that Democrats are favored to win anyway.

“Republicans have been most strategic in creating as many safe Republican districts as possible,” Jones said.

He noted that all 11 Texas’ congressional districts where racial minorities constitute a majority of voters elected Democrats to Congress. But liberal-minded Austin is the nation’s largest city not to anchor a congressional district. Instead, it’s diced into six districts that include swaths of conservative suburbs, helping ensure that all but one of the congressmen representing the state capital are Republican.

Hispanics accounted for two out of every three new Texas residents in the 2010 census. Hispanics generally vote Democratic, but a Texas Democrat hasn’t won statewide office since 1994, the nation’s longest losing streak.

The Legislature drew congressional districts based on the 2010 census, but they were never used because a federal court found they deliberately diluted the power of Hispanic voters. A three-judge panel redrew the maps used since, though they tracked many of the originals.

During years of subsequent legal battles, federal courts have repeatedly ruled against Texas maps, including in March when the state’s congressional maps were declared unconstitutional and three districts’ boundaries voided.

Kayleigh Lovvorn, a spokeswoman for Texas Attorney General Ken Paxton, whose office is defending the state in the redistricting case, declined to comment about the AP’s findings.

Voting districts aren’t the only reason that Republicans continue to hold such sway over Texas politics, though. The Hispanic population is quickly growing, but it hasn’t fully flexed its political muscle yet. Hispanic voter turnout in November was 40.5 percent. That’s up from 38.8 in the previous presidential election, but well below the 47.6 percent turnout of Hispanics throughout the country, according to the U.S. Census Bureau.


Follow Will Weissert on Twitter: