State Legislative Redistricting: The Effectiveness of Traditional Districting Principles in the 2010 Wave

Abstract

Advocates of redistricting reform believe that traditional districting principles (TDPs) were ineffective in constraining partisan gerrymanders during the 2010 redistricting wave. Yet in the wake of League of Women Voters v. Commonwealth of Pennsylvania (2018), many reformers believe the path forward consists of properly quantifying TDPs and demonstrating their violation by partisan gerrymanders. This is a viable path only insofar as TDPs materially constrain the ability of parties to design a map that delivers a seats-votes curve biased in their favor. If not, then enforcement of TDPs may change the configuration of districts without hindering partisan bias. To test whether TDPs constrain partisan gerrymanders, we analyze a complete set of state legislative maps from the 2010 redistricting wave. We measure manipulation by a low degree of overlap between parent and offspring districts which we confirm is connected to the search for partisan gain. We also examine the extent to which the effects of TDPs tend to be concentrated within few districts or spread across many districts. We find that certain legal principles—chief among them respect for communities of interest—raise overlap, possibly by limiting adjustments for partisan gain.