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In social choice theory, a center squeeze is a specific type of spoiler effect. In a center squeeze, a majority-preferred and socially-optimal candidate is eliminated in favor of a more extreme alternative under plurality-with-elimination methods like the two-round and ranked-choice runoff (RCV) rules.[1][2][3] The presence of more-extreme candidates (with strong core support from their base) "squeezes" a candidate trapped between them, starving them of the first-preference votes they need to survive in early rounds.[2][4]
The term "center squeeze" refers to candidates who are close to the center of public opinion, and as a result is not limited to centrists along the traditional political spectrum.[5] Center squeezes can occur in any situation where voters prefer candidates who hold views similar to their own.[6] By Black's theorem, the candidate who appeals most to the median voter will be the majority-preferred candidate, which means they will be elected by any method compatible with majority-rule.[2][1] However, in methods that strongly prioritize first preferences, majority-preferred candidates often get eliminated early because they aim for broad appeal rather than strong base support.[7][2][8]
Voting systems that suffer from the center-squeeze effect have a bias in favor of more extreme ideologies. This incentivizes candidates to avoid the political center,[9][4] creating unrepresentative winners and political polarization in the long run.[7][10] This effect, long predicted by social choice theorists (particularly mathematicians and economists), has since been observed empirically in Australia,[11] California,[12][13] and Maine,[14] and is well known for causing polarization in the American primary election process.
Famous examples of center-squeezes include the 2022 Alaska special election,[15][16] where moderate Nick Begich III was eliminated in the first round by right-wing Sarah Palin, despite most voters ranking Begich above Palin on their ballots. Another potential example can be found in the 2016 United States presidential election, where polls showed several alternatives defeating both Donald Trump and Hillary Clinton under a majority- or rated rule, but being squeezed out under both IRV and primary elections.[17][18]
The opposite situation (a bias toward "bland" or inoffensive candidates, particularly dark horse candidates) is substantially less common. However, such a situation arguably exists for bottom-heavy methods that elect the "least opposed" candidates, such as anti-plurality voting or Coombs' method. Methods that pass reversal symmetry treat "negative" and "positive" ratings (those near the top and bottom of a voter's ballot) equally.
Voting systems that have serious problems with center squeeze include first-preference plurality, plurality-with-primaries, two-round runoff,[2] and ranked-choice runoff voting (RCV).[2] By contrast, Condorcet and rated voting methods are not affected by such pathologies. Condorcet methods are insulated from center-squeezes by the median voter theorem, while rated voting systems like score or approval voting are protected by closely-related results.[19]
- ^ a b Merrill, Samuel (1984). "A Comparison of Efficiency of Multicandidate Electoral Systems". American Journal of Political Science. 28 (1): 23–48. doi:10.2307/2110786. ISSN 0092-5853. JSTOR 2110786.
However, squeezed by surrounding opponents, a centrist candidate may receive few first-place votes and be eliminated under Hare.
- ^ a b c d e f Merrill, Samuel (1985). "A statistical model for Condorcet efficiency based on simulation under spatial model assumptions". Public Choice. 47 (2): 389–403. doi:10.1007/bf00127534. ISSN 0048-5829.
the 'squeeze effect' that tends to reduce Condorcet efficiency if the relative dispersion (RD) of candidates is low. This effect is particularly strong for the plurality, runoff, and Hare systems, for which the garnering of first-place votes in a large field is essential to winning
- ^ Atkinson, Nathan; Ganz, Scott C. (2022-10-30). "The flaw in ranked-choice voting: rewarding extremists". The Hill. Retrieved 2023-05-14.
However, ranked-choice voting makes it more difficult to elect moderate candidates when the electorate is polarized. For example, in a three-person race, the moderate candidate may be preferred by a majority of voters to each of the more extreme candidates. However, voters with far-left and far-right views will rank the candidate in second place rather than in first place. Since ranked-choice voting counts only the number of first-choice votes (among the remaining candidates), the moderate candidate would be eliminated in the first round, leaving one of the extreme candidates to be declared the winner.
- ^ a b McGann, Anthony J.; Koetzle, William; Grofman, Bernard (2002). "How an Ideologically Concentrated Minority Can Trump a Dispersed Majority: Nonmedian Voter Results for Plurality, Run-off, and Sequential Elimination Elections". American Journal of Political Science. 46 (1): 134–147. doi:10.2307/3088418. ISSN 0092-5853. JSTOR 3088418.
As with simple plurality elections, it is apparent the outcome will be highly sensitive to the distribution of candidates.
- ^ Davis, Otto A.; Hinich, Melvin J.; Ordeshook, Peter C. (1970-01-01). "An Expository Development of a Mathematical Model of the Electoral Process". The American Political Science Review. 64 (2): 426–448. doi:10.2307/1953842. JSTOR 1953842. S2CID 1161006.
Since our model is multi-dimensional, we can incorporate all criteria which we normally associate with a citizen's voting decision process — issues, style, partisan identification, and the like.
- ^ Lewyn, Michael (2012). "Two Cheers for Instant Runoff Voting". 6 Phoenix L. Rev. 117. Rochester, NY. SSRN 2276015.
third place C is a centrist who is the second choice of Candidate A's left-wing supporters and Candidate B's right-wing supporters. ... In such a situation, C would prevail over both Candidates A ... and B ... in a one-on-one runoff election. Yet, C would not prevail under IRV because he or she finished third and thus would be the first candidate eliminated.
- ^ a b Ogren, Marcus (2024-08-01). "Candidate incentive distributions: How voting methods shape electoral incentives". Electoral Studies. 90: 102799. arXiv:2306.07147. doi:10.1016/j.electstud.2024.102799. ISSN 0261-3794.
- ^ Lewyn, Michael (2012). "Two Cheers for Instant Runoff Voting". 6 Phoenix L. Rev. 117. Rochester, NY.
third place Candidate C is a centrist who is the second choice of Candidate A's left-wing supporters and Candidate B's right-wing supporters. ... In such a situation, Candidate C would prevail over both Candidates A ... and B ... in a one-on-one runoff election. Yet, Candidate C would not prevail under IRV because he or she finished third and thus would be the first candidate eliminated
- ^ Robinette, Robbie (2023-09-01). "Implications of strategic position choices by candidates". Constitutional Political Economy. 34 (3): 445–457. doi:10.1007/s10602-022-09378-6. ISSN 1572-9966.
- ^ Merrill, Samuel (1984). "A Comparison of Efficiency of Multicandidate Electoral Systems". American Journal of Political Science. 28 (1): 23. doi:10.2307/2110786. ISSN 0092-5853.
However, squeezed by surrounding opponents, a centrist candidate may receive few first-place votes and be eliminated under Hare.
- ^ Mussel, Johanan D.; Schlechta, Henry (2023-07-21). "Australia: No party convergence where we would most expect it". Party Politics. doi:10.1177/13540688231189363. ISSN 1354-0688.
- ^ Kousser, Thad; Phillips, Justin; Shor, Boris (2016). "Reform and Representation: A New Method Applied to Recent Electoral Changes*". Political Science Research and Methods. 6 (4): 809–827. doi:10.1017/psrm.2016.43. ISSN 2049-8470. SSRN 2260083.
neither the Citizens Redistricting Commission nor the top-two primary immediately halted the continuing partisan polarization of California's elected lawmakers or their drift away from the average voter
- ^ Kousser, Thad. "California's jungle primary sets up polarized governor's race for November". The Conversation. Retrieved 2018-06-23.
The idea was that by opening up primaries to all voters, regardless of party, a flood of new centrist voters would arrive. That would give moderate candidates a route to victory .. Candidates did not represent voters any better after the reforms, taking positions just as polarized as they did before the top two. We detected no shift toward the ideological middle.
- ^ "The Effect of Ranked-Choice Voting in Maine | MIT Election Lab". electionlab.mit.edu. Retrieved 2024-07-25.
One of the main claims made by reformers about RCV is that it will make campaigns more civil, as campaigns will have the incentive to seek the second-place vote of supporters of different candidates. To study this claim, I first conducted a difference-in-differences analysis on independent expenditures for and against candidates. In this analysis, I found that negative spending increased significantly in Maine following the implementation of ranked-choice voting, casting doubt on the claim that RCV makes campaigns more civil. To provide more evidence, I also created a dataset of all Facebook advertisements that mentioned any congressional candidates for 2018, the first year that RCV was used in Maine. I then conducted a sentiment analysis to find each advertisement's sentiment (whether it was negative or not). I then used genetic matching to approximate an experiment to find the impact of RCV on civility. In doing so, I found that the 2018 campaign was even more negative than in paired districts around the country.
- ^ Graham-Squire, Adam; McCune, David (2022-09-11). "A Mathematical Analysis of the 2022 Alaska Special Election for US House". p. 2. arXiv:2209.04764v3 [econ.GN].
Since Begich wins both … he is the Condorcet winner of the election … AK election also contains a Condorcet loser: Sarah Palin. … she is also a spoiler candidate
- ^ Atkinson, Nathan; Ganz, Scott C. (2022-10-30). "The flaw in ranked-choice voting: rewarding extremists". The Hill. Retrieved 2023-05-14.
However, ranked-choice voting makes it more difficult to elect moderate candidates when the electorate is polarized. For example, in a three-person race, the moderate candidate may be preferred to each of the more extreme candidates by a majority of voters. However, voters with far-left and far-right views will rank the candidate in second place rather than in first place. Since ranked-choice voting counts only the number of first-choice votes (among the remaining candidates), the moderate candidate would be eliminated in the first round, leaving one of the extreme candidates to be declared the winner.
- ^ Potthoff, Richard F.; Munger, Michael C. (November 2021). "Condorcet Loser in 2016: Apparently Trump; Condorcet Winner: Not Clinton?". American Politics Research. 49 (6): 618–636. doi:10.1177/1532673X211009499. ISSN 1532-673X.
- ^ Igersheim, Herrade; Durand, François; Hamlin, Aaron; Laslier, Jean-François (2022). "Comparing Voting Methods : 2016 US Presidential Election". European Journal of Political Economy. 71. doi:10.1016/j.ejpoleco.2021.102057.
- ^ Laslier, Jean-François; Sanver, Remzi, eds. (2010). Handbook on Approval Voting. Studies in Choice and Welfare. Heidelberg: Springer Berlin. doi:10.1007/978-3-642-02839-7. ISBN 978-3-642-02839-7.