American Politics Research Volume XX Number X Month XXXX xx-xx © 2009 SAGE Publications 10.1177/1532673X08326385 http://apr.sagepub.com hosted at http://online.sagepub.com 1 Are Mapmakers Able to Target and Protect Congressional Incumbents? The Institutional Dynamics of Electoral Competition Chad Murphy Antoine Yoshinaka University of California, Riverside Can those in charge of redistricting foster electoral competitiveness by targeting some congressional incumbents while protecting others from potent competi- tion? We provide an answer by presenting the dynamic redistricting thesis, which holds that the type of redistricting plan and the time passed since its enactment affect the emergence of high-quality congressional candidates. We demonstrate that the effect of redistricting on competition depends on whether incumbents belong to the party that controlled the redistricting process. We show that partisan plans have predictable systematic effects, with incumbents in the minority more likely to face strong opponents. Moreover, the effect of redistricting on competi- tion is highest at the beginning of the 10-year redistricting cycle and diminishes in a nonlinear fashion over the course of the cycle. The implications of our theory and findings for democracy are apparent: Institutions are an important determi- nant of the variation of electoral competition across time and space. Keywords: congressional elections; electoral competition; incumbency; apportionment; gerrymandering; redistricting; representation; dynamic redistricting thesis “[T]he democratic method is that institutional arrangement for arriving at political decisions in which individuals acquire the power to decide by means of a competitive [italics added] struggle for the people’s vote.” Schumpeter (1976, p. 269) Perhaps more than any other attribute, democracy depends on vigorous competition to ensure the people’s will prevails. To formulate meaningful preferences, citizens must have the opportunity to choose among viable doi:10.1177/1532673X08326385 American Politics Research OnlineFirst, published on February 19, 2009 as