Electoral Redistricting, Incumbency Advantage, and Endogenous Candidate Selection

In this paper, we examine the effects of redrawing district boundaries (redistricting) on political parties' candidate selection strategies. This study is distinct from previous studies in two regards. First, we focus on a unique natural experimental setting in Australia, where a non-partisan committee determines redistricting exogenously to the causal mechanism constituting the process of candidate selection. Second, we develop a formal model of endogenous candidate selection, which assumes strategic interactions by a party that won a seat in the previous election and a party that was defeated, and examine how an exogenous shock (i.e., redistricting) affects their decisions. Our empirical results based on the Australian Lower House election data for the period of 1990-2010 are consistent with an incumbency disadvantage hypothesis deduced from our model; namely, the magnitude of redistricting significantly increases the probability that the winning party will replace their incumbent legislator with a fresh candidate.