Political Control Over Redistricting and the Partisan Balance in Congress

We estimate the impact of a political party’s ability to unilaterally redistrict Congressional seats upon partisan seat share allocations in the U.S. House of Representatives. Controlling for stateXdecade and year effects, we find an 8.2 percentage point increase in the Republican House seat share in the three elections following Republican control over redistricting in the past two decades. We only find significant effects for Democrats in large states. Effects are one half of the average seat gap between the parties in the 2010s. Differences across parties reflect more denied trifectas due to an opposite party governor in Democratic states and greater impacts for Republicans in small states. Differences do not reflect a rise in racial gerrymandering.