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

David McCune, Matthew I. Jones, Andy Schultz, Adam Graham-Squire, Ismar Volic, Belle See, Karen Xiao, Malavika Mukundan

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.

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

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.
Paper Structure (15 sections, 45 figures, 7 tables)

This paper contains 15 sections, 45 figures, 7 tables.

Table of Contents

  1. Introduction
  2. Descriptions of Voting Methods
  3. Overview of the Work of Atkinson et al.
  4. Description of Methodology and Models
  5. Results
  6. Moderating effects of IRV and Condorcet under the six models
  7. Variations in moderating effects by voter distributions
  8. Discussion
  9. Conclusion
  10. Winner Ideological Position Histograms
  11. Average Distance from Median Voter Sample Summary Statistics
  12. Relative Increase in Distance from Median Voter Images
  13. Relative Differences and Changes for all models
  14. State Distribution Summary Statistics
  15. Data from noise tuning simulations

Figures (45)

  • Figure 1: A figure taken from AFG, showing the voter distribution (left), distribution of IRV winner positions (center), and distribution of Condorcet winner positions (right) in Arizona. Figure reproduced with permission of the authors.
  • Figure 2: Trimodal voter distributions for five sample states.
  • Figure 3: Bimodal voter distributions for five sample states.
  • Figure 4: Histograms showing the ideological positions of Condorcet and IRV winners across 100,000 simulations in Michigan, using 4-candidate elections with the bimodal voter distribution.
  • Figure 5: The relative difference of the average distance of the IRV winner and the average distance of the Condorcet winner to the median voter.
  • ...and 40 more figures

Theorems & Definitions (1)

  • Example 1