When Considering Partisanship, Analysis Suggests Texas Congressional Redistricting Plan is Unconstitutional

Study by UH Hobby School Reviews Partisan Gerrymandering


A new analysis of Texas political boundaries by the University of Houston Hobby School of Public Affairs found the state’s Congressional redistricting plan would likely be found unconstitutional if partisan gerrymandering were considered, while the state Senate and House redistricting plans appear to fall within constitutional guidelines if solely considering partisanship.

The current court challenge to Texas’ redistricting plans for Congressional and state House seats is based on racial gerrymandering, not whether the lines were drawn to provide a partisan advantage.

The analysis of the Texas redistricting plans relied on a new statistical measure of partisan gerrymandering used by the Democratic plaintiffs in a Wisconsin case pending before the U.S. Supreme Court. That case is focused on whether there is a threshold for partisan gerrymandering that, once crossed, makes a redistricting plan unconstitutional.

For the analysis, Hobby School researchers considered Texas Legislative and Congressional races in 2012, 2014 and 2016, calculating the efficiency gap, a measure of the systemic advantage to one party or the other. The efficiency gap includes the number of votes “wasted” on a particular candidate because of efforts to pack a district with either Democratic or Republican voters.   

Jim Granato, executive director of the Hobby School, said it’s not a surprise for the party in power to benefit from redrawing political boundaries.

“It is well accepted that the party in power benefits from redistricting,” Granato said.

Mark P. Jones, political scientist at Rice University and a research associate at the Hobby School, said the analysis found the Texas redistricting plan provided Republicans with 3.2 more seats in Congress than they would have earned under a neutral redistricting plan. According to the efficiency gap measure, anything above 2 seats is unconstitutional.

“This is 1.2 seats more than the Republicans would have received under a plan that did not rely on extreme partisan gerrymandering,” he said.

In the Texas House districts, Renée Cross, associate director of the Hobby School, said the efficiency threshold is anything above 12 seats, and the analysis found that state House districts averaged 6.9 seats during the period of 2012-2016. A smaller gap was found in the Texas Senate with a varying threshold determined by the number of senators elected in a given year.

“While partisan gerrymandering is a common practice, the question is when does it become extreme?” Cross said.

This fall the Hobby School will release a report on partisan gerrymandering in Texas, which will contain a series of sensitivity tests of the efficiency gap measure, with a particular focus on different methods for imputing the electoral support for Democrats and Republicans in uncontested seats. 

Preliminary analysis indicates the efficiency gap measure is sensitive to the assumptions made in the models used to impute Democratic and Republican support in uncontested legislative contests, as well as to the frequency of contested seats where the losing party is represented by a gadfly candidate.  As a consequence, the efficiency gap values in a given election can vary depending on the imputation methods employed.



Read more about the analysis here.


Cover photo: Getty images