Candidate Moderation under Instant Runoff and Condorcet Voting: Evidence from the Cooperative Election Study

TL;DR

This paper compares instant-runoff voting and Condorcet methods in promoting candidate moderation, finding that under realistic voter behavior, their moderating effects are similar, challenging previous theoretical conclusions.

Contribution

It introduces new models based on survey data that incorporate realistic voter behavior, showing that the moderating advantage of Condorcet methods diminishes in practical scenarios.

Findings

Condorcet methods produce more moderate winners in idealized models.

Realistic voter behavior reduces differences between IRV and Condorcet outcomes.

Moderating effects of Condorcet methods may be less significant in real-world elections.

Abstract

This article extends the analysis of Atkinson, Foley, and Ganz in "Beyond the Spoiler Effect: Can Ranked-Choice Voting Solve the Problem of Political Polarization?". Their work uses a one-dimensional spatial model based on survey data from the Cooperative Election Survey (CES) to examine how instant-runoff voting (IRV) and Condorcet methods promote candidate moderation. Their model assumes an idealized electoral environment in which all voters possess complete information regarding candidates' ideological positions, all voters provide complete preference rankings, etc. Under these assumptions, their results indicate that Condorcet methods tend to yield winners who are substantially more moderate than those produced by IRV. We construct new models based on CES data which take into account more realistic voter behavior, such as the presence of partial ballots. Our general finding is that under more realistic models the differences between Condorcet methods and IRV largely disappear, implying that in real-world settings the moderating effect of Condorcet methods may not be nearly as strong as what is suggested by more theoretical models.