Gerrymandering Incumbency: Does Nonpartisan Redistricting Increase Electoral Competition?

The State of Democracy in the Americas 2021: Democracy in Times of Crisis

“…142 Other researchers have shown that even drawing new districts in a non-partisan way would only marginally affect incumbent re-election prospects given the larger effects of demographic sorting and polarization. 143 Polarization is given even more powerful effects by a trend towards negative partisanship, in which voters make their choices 'based on hostility toward the opposing party and its leaders'. 144 The combination of these factors potentially undermines the foundations of healthy democracy.…”

Do Redistricting Commissions Avoid Partisan Gerrymanders?

“…We use these VTD shapefiles to generate 10,000 alternative congressional maps for each state using a graph partitioning process proposed by Magleby & Mosesson, (2018). While scholars anticipated the possibility of drawing electoral maps using computers for decades (see Bozkaya et al, 2003; Browdy, 1990; Chou and Li, 2006; Cirincione et al, 2000; Fryer & Holden, 2011; Garfinkel and Nemhauser, 1970; Nagel, 1965; Vickery, 1961; Weaver & Hess, 1963), methodological and computation advances in the last several years have made computer-drawn maps a reality (see, e.g., Chen & Cottrell, 2016; Chen & Rodden, 2013; Cho & Liu, 2016; Henderson et al, 2018).…”

“…On the other hand, there are also studies that reach less optimistic conclusions (Cottrill, 2012; Henderson et al, 2018; Kousseser et al, 2018; Miller and Grofman, 2013). Chen & Cottrell, (2016) analysis of all states’ congressional districting plans found that California’s independent commission produced, more so than any other state, bonus seats for Democrats compared to expectations from computer-generated neutral districting.…”

“…Chen & Cottrell, (2016) analysis of all states’ congressional districting plans found that California’s independent commission produced, more so than any other state, bonus seats for Democrats compared to expectations from computer-generated neutral districting. On the topic of electoral competition, Henderson et al (2018) found that the districting plans created by independent commissions insulated incumbents similarly to the districting plans created by state legislatures. And then there is the essentially ignored advisory commission plan that preceded Virginia’s legislature taking over the process of redrawing the State’s congressional districts.…”

“…Although it is increasingly common to evaluate partisan bias in a given district map by comparing it to a set of computer-generated maps (e.g. Chen & Cottrell, 2016; Cho & Liu, 2016; Henderson et al, 2018; Magleby & Mosesson, 2018), the literature on redistricting commissions has compared districting lines drawn by commissions to those drawn by state legislatures. 3 Indeed, when we look at cross-state comparisons of commission maps to those produced by partisan legislatures, we find that commissions generally produce less bias.…”