Redistricting principles and incumbency protection in the US Congress

Critics of congressional redistricting have argued that recent legislative gerrymandering severely undermines electoral competitiveness to the point of violating constitutional equal protection standards. In this paper, we assess how states' redistricting plans vary in incumbency protection. Particularly, we evaluate whether redistricting principles and processes had any measurable consequence in incumbency protection in the 2000 redistricting cycle. We first report substantial regional variation across states in the principles formally noted in state redistricting laws. We then report results showing that some traditional, "politically neutral" redistricting principles and less politicized processes significantly diminish incumbency protection. Our results indicate significant incumbency gerrymandering across states in the recent cycle; however, states have significantly less incumbency protection when they specify specific population- and politically-based principles while suppressing elected officials' agenda setting influence in the districting process. (c) 2005 Elsevier Ltd. All rights reserved.