Strategic Redistricting By Faruk Gul and Wolfgang Pesendorfer

Regional differences in population growth periodically necessitate changing congressional districts’ boundaries. This redistricting process creates an intense conflict between political parties. In this paper, we analyze the redistricting process for the House of Representatives and the interaction between redistricting and policy choice. States face few constraints when setting their congressional districts’ boundaries: congressional districts must have the same population as each other and must be contiguous, which, in practice, is a fairly permissive constraint. In a well-known example, Illinois’s fourth congressional district combines two disjoint areas through a very narrow strip. In short, a political party that controls a state’s political institutions has wide latitude in designing a favorable electoral map. In some cases, independent commissions rather than individual parties control the redistricting process. We ignore such bipartisan redistricting and assume that a single party controls each state’s political institutions. Bipartisan redistricting can be incorporated into our model by giving parties control of less than 100 percent of the districts and interpreting the remainder as an exogenous nonpartisan redistricting plan. We model the strategic interaction between the two parties as a zero-sum game under uncertainty. We recognize that parties and different agents within parties may evaluate election outcomes in different ways; incumbents may want to protect their own seats, while other party members may wish to maximize the number of representatives. We focus, however, on the most important election outcome: majority control in the House of Representatives. Our model combines Downs-Hotelling style party competition with redistricting. We assume that the two parties’ supporters have different distributions of policy preferences (i.e., ideal points). The overall distribution of ideal points is a θ-weighted average of these two distributions where θ is the proportion of Republicans in the population. In Section II, we fix the party policies and study redistricting in isolation. Voter characteristics and an uncertain aggregate state determine the fraction of Republican voters in the population. Parties observe voter characteristics