Redistricting principles and incumbency protection in the U.S. 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.     

Components of partisan bias originating from single-member districts in multi-party systems: An application to Mexico

We extend the estimation of the components of partisan bias—i.e., undue advantage conferred to some party in the conversion of votes into legislative seats—to single-member district systems in the presence of multiple parties. Extant methods to estimate the contributions to partisan bias from malapportionment, boundary delimitations, and turnout are limited to two-party competition. In order to assess the spatial dimension of multi-party elections, we propose an empirical procedure combining three existing approaches: a separation method (Grofman et al. 1997), a multi-party estimation method (King 1990), and Monte Carlo simulations of national elections (Linzer, 2012). We apply the proposed method to the study of recent national lower chamber elections in Mexico. Analysis uncovers systematic turnout-based bias in favor of the former hegemonic ruling party that has been offset by district geography substantively helping one or both other major parties.     

Tools for identifying partisan gerrymandering with an application to congressional districting in Pennsylvania

In League of Women Voters v. Commonwealth of Pennsylvania (2018) the Pennsylvania Supreme Court struck down as a “severe and durable” partisan gerrymander the congressional map drawn by Republicans in 2011 and used in elections from 2012-2016. It did so entirely on state law grounds after a three-judge federal court had rejected issuing a preliminary injunction against the plan. After Pennsylvania failed to enact a lawful remedy plan of its own (due to total disagreement as to how to proceed between the newly elected Democratic governor and the still Republican-controlled legislature), the Court then ordered into place for the 2018 election a map of its own drawn for it by a court-appointed consultant. In a split court, the Court map was endorsed only by judges with Democratic affiliations. Here we compare the 2011 and 2018 congressional maps in terms of a variety of proposed metrics for detecting partisan gerrymandering. We also examine the remedy map proposed by a group of Republican legislators and that proposed by the Democratic governor. We conclude that the 2011 map was a blatant and undisguised pro-Republican gerrymander. Moreover, the remedy map proposed by Republican legislators was a covert pro-Republican gerrymander (what we refer to as a “stealth gerrymander”). The Democratic governor's proposed plan cannot be classified as a pro-Democratic gerrymander and indeed has, if anything, a slight pro-Republican tilt. The 2018 court-drawn remedial map, by all measures, was not a gerrymander.