Pack-Crack-Pack: Gerrymandering with Differential Turnout

This paper studies the manipulation of electoral maps by political parties, known as gerrymandering. At the core of our analysis is the recognition that districts must have the same population size but only voters matter for electoral outcomes. We propose a model of gerrymandering that allows for heterogeneity in turnout rates across individuals. We show how this modifies the gerrymandering strategies: the novel pattern is to pack-crack-pack along the turnout dimension. That is, parties benefit from packing their supporters when they have too low turnout rate as well as their opponents when they have too high turnout rate. In between, they create cracked districts that mix moderate-to-high-turnout supporters with lower-turnout opponents. This produces testable empirical implications about the link between partisan support, turnout rates, and electoral maps. Using a novel empirical strategy that relies on the comparison of maps proposed by Democrats and Republicans during the 2020 redistricting cycle in the US, we bring such empirical implications to the data and find support for them.