Gerrymandering Incumbency: Does Non-Partisan Redistricting Increase Electoral Competition?

Abstract

Many political advocacy groups, journalists, and scholars view decennial redistricting as a major force in weakening the representational link between voters and officeholders by helping insulate legislative incumbents from electoral defeat. Motivated by this concern, reformers in a number of states have proposed giving control over redistricting to 'politically-neutral' independent commissions. Freed from partisan and electoral pressures, independent redistrictors would be expected to draw districts without giving favor to parties or their incumbents. In this study, we analyze two novel datasets of alternative redistricting plans, to evaluate whether maps drawn by independent commissions are more electorally competitive than those produced by party-controlled legislatures, compared to the proposals that could have been adopted. We find that the redistricting process on the margin, helps sustain the electoral security of incumbents. Yet, counter to reformers' expectations, we find that independent redistrictors produce virtually the same degree of insulation as plans devised in legislatures or by politician commissions. Overall, our results suggest caution in overhauling state redistricting institutions to increase electoral competition: independent commissions may not be as politically-neutral as theorized.

Keywords: redistricting, independent commissions, elections, gerrymandering, simulations