Mathematics of Nested Districts: The Case of Alaska

TL;DR

This paper analyzes how nesting rules in Alaska's districting can significantly influence partisan outcomes, showing that pairing choices alone can swing election results by several seats.

Contribution

It provides a quantitative assessment of the impact of nesting rules on districting outcomes, highlighting the partisan effects of pairing choices in Alaska.

Findings

Nesting rules can cause a 4-5 seat swing in Alaska's Senate.

Partisan effects of pairing choices are comparable to unconstrained plans.

Insights into partisan latitude under nesting and contiguity rules.

Abstract

In eight states, a "nesting rule" requires that each state Senate district be exactly composed of two adjacent state House districts. In this paper we investigate the potential impacts of these nesting rules with a focus on Alaska, where Republicans have a 2/3 majority in the Senate while a Democratic-led coalition controls the House. Treating the current House plan as fixed and considering all possible pairings, we find that the choice of pairings alone can create a swing of 4-5 seats out of 20 against recent voting patterns, which is similar to the range observed when using a Markov chain procedure to generate plans without the nesting constraint. The analysis enables other insights into Alaska districting, including the partisan latitude available to districters with and without strong rules about nesting and contiguity.