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Acenter squeeze is a kind ofspoiler effect shared by rules like thetwo-round system,plurality-with-primaries, andinstant-runoff voting (IRV).[1] In a center squeeze, themajority-preferred andsocially optimal candidate is eliminated in favor of a moreextreme alternative before having a chance to face another candidate in a one-on-one race.[2][3] Systems with center-squeeze are sometimes calledcentrifugal ("center-fleeing") because they encouragepolitical polarization.[4]
Candidates focused on appealing to a smallbase ofcore supporters can "squeeze" broadly-popular candidates trapped between them out of the race, by splitting thefirst-round vote needed to survive earlier rounds.[1][5][6] This effect was first predicted bysocial choice theorists in the 1940s and 50s, and has since been documented in various countries usingplurality-style electoral systems.
Famous examples of center squeezes include theAlaska's 2022 special election (whereNick Begich III was eliminated in the first round bySarah Palin)[7] as well as the2007 French presidential election, where moderate liberalFrançois Bayrou was eliminated by left-populistSégolène Royal, allowing the right-wingNicolas Sarkozy to win the second round.[8][9]
Center squeezes are a kind ofspoiler effect in which the majority-preferred candidate is eliminated before the final round of an election.[10][11] Candidates focused on appealing to a smallbase ofcore supporters can squeeze Condorcet winners out of the race, by splitting thefirst-round vote needed to survive earlier rounds.[12][13]
ByBlack's median-voter theorem, the candidate who appeals most to the median voter will be themajority-preferred candidate, which means they will be elected byany method compatible with majority-rule.[1][10] However, in methods that strongly prioritize first preferences, these candidates are often eliminated early on because they aim for broad appeal rather than strongbase support.[1][14][15]
The "center" in "center squeeze" refers to candidates who are close to the center of public opinion, and is not limited tocentrists along a traditional, one-dimensionalpolitical spectrum.[16] A center squeeze can occur in any situation where voters prefer candidateswho hold views similar to their own.[15]
Voting systems that suffer from the center-squeeze effect incentivize candidates to avoid the political center,[13][17][14] creating political polarization in the long run.[17][14][10] As a result, rules like RCV can lead to polarization even if center squeezes seem empirically rare, because the electoral system provides few incentives encouraging moderates to run for office in the first place.[17][14][18]
Center-squeeze has been observed inAustralia,[19][20][21]Maine,[22]Fiji,[23][24] and variousUS cities,[25] all of which useranked-choice voting, in addition toCalifornia (which usesnonpartisan primaries).[26][27]
Center squeeze is a major feature of two-party systems usingprimaries or other multiple-round systems.[12] In these methods, candidates must focus on appealing to theircore supporters to ensure they can make it past the first round, where only first-preferences count.[12]
If voters assign scores to candidates based on ideological distance,score voting will always select the candidate closest to somecentral tendency of the voter distribution. As a result, while score voting does not always elect the candidate closest to the median voter, it often behaves like methods that do.[28][29] Under most models of strategic voting,spoilerproof cardinal methods tend to behave likeapproval voting and thus converge on the Condorcet winner.[30][31][32][33]
The opposite situation—a bias in favor of bland, inoffensive, or unknown candidates—is not common in any widely-used voting rules. However, it can occur for "negative" voting methods that choose candidates with the least opposition, likeanti-plurality,D21 – Janeček, orCoombs' method.[34]
| Start: | Mid-Start: | Mid-End: | End: |
|---|---|---|---|
| 33.4% | 17.2% | 13.4% | 35.9% |
In Alphabet Land, voters are divided based on how names should be arranged on lists. thinks names should always be in alphabetical order; thinks they should be in reverse-alphabetical order; and thinks the order should be randomized. In this example, voters' happiness with the outcome fallslinearly with the distance (number of letters) between the voter and the candidate.
Because is preferred to both and in head-to-head match-ups, is themajority-preferred (Condorcet) winner. is thesocially-optimal winner as well.[29] Thus, is the "best" or "most popular" candidate under both common metrics of candidate quality insocial choice.[10]
wins under a single-round of FPP, with 35.9% of voters choosing them as their favorite. However, over substantially more voters considered to be their least favorite, with 63.1% of voters preferring. is elected, despite an overwhelming two-thirds majority preferring.
Ranked-choice voting (RCV) tries to address vote-splitting in FPP by replacing it with a series of FPP elections, with the loser being eliminated in each round.[35][36]
The first round of the election is the same as the FPP election. has the leastfirst preferences and is therefore eliminated. Their votes are reassigned to and, according to their ballot. In the second round, enough voters who preferred as their first choice took as their second choice and wins the election. RCV thus fails to have a substantial moderating impact, instead causing only a swing from one extreme to the other.[37]
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The2022 Alaska special election seat was an example of a center squeeze, whereNick Begich III was eliminated in the first round byright-wing spoilerSarah Palin,[7][39] despite a majority of voters preferring Begich to either one of his opponents.[7][40] The ranked-choice runoff election involved oneDemocrat (Mary Peltola) and twoRepublicans (Sarah Palin andNick Begich III). Because the full ballot data for the race was released,social choice theorists were able to confirm that Palin spoiled the race for Begich, with Peltola winning the race as a result of severalcounter-intuitive behaviors that tend to characterize center-squeeze elections.[40][7]
The election produced a winner opposed by a majority of voters, with a majority of voters ranking Begich above Peltola and Palin,[41][7][39] and more than half giving Peltola no support at all.[41][7] The election was also notable as ano-show paradox, where a candidate is eliminated as a result of votes cast insupport of their candidacy. In this case, ballots ranking Palin first and Begich second instead allowed Peltola to win.[7][42][39]
Manysocial choice theorists criticized the ranked-choice runoff procedure for itspathological behavior.[43][7] Along with being a center squeeze, the election was anegative voting weight event,[42] where a voter's ballot has the opposite of its intended effect (e.g. where a candidate would needmore votes to lose).[42][44] In this race, Peltola would have lost if she had received more support from Palin voters,[45][7][41] and won as a result of 5,200 ballots that ranked her last (after Palin then Begich).[42][7] However,social choice theorists were careful to note the results likely would have been the same under Alaska's previous primary system as well. This led several to recommend replacing the system with any one of severalalternatives without these behaviors, such asSTAR,approval, orCondorcet voting.[40][41]
The2009 Burlington mayoral election was held in March 2009 for the city ofBurlington, Vermont, and serves as an example of a four-candidate center squeeze. This was the second mayoral election since the city's 2005 change toranked-choice runoff voting, after the2006 mayoral election.[46] In the 2009 election, incumbentBurlington mayorBob Kiss won reelection as a member of theVermont Progressive Party,[47] defeating Kurt Wright in the final round with 48% of the vote.[48]
The election results were criticized bymathematicians andvoting theorists for severalpathologies associated with RCV. These included ano-show paradox, where Kiss won only as a result of 750 votes ranking Kiss in last place.[49][50][51] Severalelectoral reform advocates branded the election a failure after Kiss was elected despite 54% of voters voting for Montroll over Kiss,[52][53] violating themajority-rule principle.[54][55][56] Later analyses showed the race was spoiled, with Wright pulling moderate votes away from Montroll, who would have beat Kiss in a one-on-one race.[55][57]
The controversy culminated in a successful 2010initiative that repealed RCV by a vote of 52% to 48%,[58][59] a 16-point shift from the 64% who had supported the 2005 ratification.[46] The results of every possible one-on-one election are as follows:
| Party | Candidate | vs. Simpson | vs. Smith | vs. Wright | vs. Kiss | Win : Loss |
|---|---|---|---|---|---|---|
 | Andy Montroll (D) | 6262 (Montroll) – 591 (Simpson) | 4570 (Montroll) – 2997 (Smith) | 4597 (Montroll) – 3664 (Wright) | 4064 (Montroll) – 3476 (Kiss) | 4 W : 0 L |
 | Bob Kiss (P) | 5514 (Kiss) – 844 (Simpson) | 3944 (Kiss) – 3576 (Smith) | 4313 (Kiss) – 4061 (Wright) | 3 W : 1 L | |
 | Kurt Wright (R) | 5270 (Wright) – 1310 (Simpson) | 3971 (Wright) – 3793 (Smith) | 2 W : 2 L | ||
| Dan Smith (I) | 5570 (Smith) – 721 (Simpson) | 1 W : 3 L | ||||
 | James Simpson (G) | 0 W : 4 L | ||||
This leads to an overall preference ranking of:
Montroll was therefore preferred over Kiss by 54% of voters, over Wright by 56% of voters, over Smith by 60%, and over Simpson by 91% of voters.[60][61]
Another possible example is the2016 United States presidential election, where polls found several alternatives includingBernie Sanders andGary Johnson defeating bothDonald Trump andHillary Clinton under amajority- orrated-voting rules but being squeezed out by both RCV and theprimary election rules.[28][62]
Election law scholarNed Foley criticized thetwo-round system variant used in the United States, which has been described as a first round ofprimaries before ade-facto runoff,[63][64] for creating a center squeeze in the 2024 presidential election and thus contributing topolitical polarization. Foley noted both the existing primary system and a hypothetical election instant-runoff system would lead to the election ofDonald Trump by eliminatingNikki Haley, the majority-preferred (Condorcet) candidate according to polling.[65][66]
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
However, squeezed by surrounding opponents, a centrist candidate may receive few first-place votes and be eliminated under Hare.
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.
As with simple plurality elections, it is apparent the outcome will be highly sensitive to the distribution of candidates.
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
However, squeezed by surrounding opponents, a centrist candidate may receive few first-place votes and be eliminated under Hare.
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.
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
As with simple plurality elections, it is apparent the outcome will be highly sensitive to the distribution of candidates.
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.
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.
Fiji's objective of ameliorating ethnic divisions by the adoption of AV was not successful. In elections in 1999 and 2001, moderate parties would have fared better under a proportional representation system
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
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.
By eliminating the squeezing effect, Approval Voting would encourage the election of consensual candidates. The squeezing effect is typically observed in multiparty elections with a runoff. The runoff tends to prevent extremist candidates from winning, but a centrist candidate who would win any pairwise runoff (the "Condorcet winner") is also often "squeezed" between the left-wing and the right-wing candidates and so eliminated in the first round.
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.
It's a good thing for Peltola that she didn't attract more Palin voters—she'd have lost [...] The strangeness continues. Peltola could have actually gotten more 1st choice votes in this election and caused herself to lose. How's that? Let's look. [...] Imagine if Peltola reached across the aisle and spoke directly to Palin voters. Imagine that she empathized with their position and identified issues they cared about that Palin and even Begich ignored. And let's say that as a consequence, Peltola got the first-choice votes of between 5,200 and 8,500 voters who would have otherwise ranked only Palin. What happens as a result? Palin would have gotten eliminated in the first round and Peltola would still not be able to beat Begich.
4. How did this change to IRV come about?
Over 64% of Burlington voters voted in favor of the IRV Charter amendment in March 2005, and it went into effect on May 12, 2005, when the governor signed the ratification bill, H.505, which had been passed by both the House and Senate.
A display of non-monotonicity under the Alternative Vote method was reported recently, for the March 2009 mayoral election in Burlington, Vermont.
Although the Democrat was the Condorcet winner (a majority of voters preferred him in all two way contests), he received the fewest first-place votes and so was eliminated ... 2009 mayoral election in Burlington, VT, which illustrates the key features of an upward monotonicity failure
Montroll was favored over Republican Kurt Wright 56% to 44% ... and over Progressive Bob Kiss 54% to 46% ... In other words, in voting terminology, Montroll was a 'beats-all winner,' also called a 'Condorcet winner' ... However, in the IRV election, Montroll came in third! ... voters preferred Montroll over every other candidate ... Montroll is the most-approved
a majority of voters liked the centrist candidate Montroll better than Kiss, and a majority of voters liked Montroll better than Wright ... yet Montroll was tossed in the first round.
K was elected even though M was a clear Condorcet winner and W was a clear Plurality winner.
Finally, we should not discount the role of primaries. When we look at the range of countries with first-past-the-post (FPTP) elections (given no primaries), none with an assembly larger than Jamaica's (63) has a strict two-party system. These countries include the United Kingdom and Canada (where multiparty competition is in fact nationwide). Whether the U.S. should be called 'FPTP' itself is dubious, and not only because some states (e.g. Georgia) hold runoffs or use the alternative vote (e.g. Maine). Rather, the U.S. has an unusual two-round system in which the first round winnows the field. This usually is at the intraparty level, although sometimes it is without regard to party (e.g. in Alaska and California).
In effect, the primary system means that the USA has a two-round runoff system of elections.
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