Who Wins RCV Races?
Who Wins RCV Races?
In this section we explore how RCV has worked in practice in the United States. We summarize research on how RCV has worked to remove the spoiler effect and on the tendency of RCV in single-winner seats to elect candidates with majority support. We also assess RCV in practice on some more technical grounds, namely monotonicity and its tendency to elect Condorcet winners.
Majority Winners
A key reason we need RCV is that our current system often elects winners with less than majority support, or less than 50% of the votes.
- Since 1992, 49 senators from 27 states have been elected with less than 50 percent support.
Harrow, J. & Shi, V. 2019. The magic of majority rule in elections. The Hill.
- Primary elections are also often decided with small pluralities. The chart below shows plurality wins in primary elections for U.S. House of Representatives races in 2018. In some highly-contested races, winners received as little as 22% of the vote -- meaning 78% of people voted against them.
https://e.infogram.com/f4ff3f81-be7b-46c2-8b40-fa5850fdaeef?src=embed2018 Plurality Winsnoborder:none;allowfullscreen5507460
- There have been 204 single-winner ranked choice elections in the U.S. which included at least 3 candidates. In 96 of these (or 47%), a majority winner was identified in the first round. The remaining 108 races went into the instant runoff before declaring a winner.
- Sometimes, the winner of a single-winner RCV election does not have a majority of total votes cast in the first round. A winner is declared when a candidate has a majority of votes which are active in that round of counting, which excludes ballots which have become exhausted. This has occurred in 63 single-winner RCV elections in the U.S. As noted by Burnett and Kogan, ballot exhaustion is sometimes due to jurisdiction limiting the maximum number of rankings to three. 53 out of 63 elections in which the winner had fewer than 50% of first-round votes occurred in elections which limited voters to three rankings. You can learn more about the majority criterion with RCV in our FAQ.
RCV and Incumbents
- RCV appears to have a neutral effect on incumbents. A FairVote report on incumbency in the Bay Area of California shows that incumbents are re-elected at the same rate both with and without RCV.
FairVote California. October 2017. RCV and Incumbency in the Bay Area.
Come-From-Behind Winners
- There have been 15 RCV races in the U.S. which were won by a candidate other than the first-round leader. That’s 4.2% of the 353 single-winner RCV races since 2004.
- Of those 15 races, 14 were won by the candidate who began in second place. One race was won by the candidate who was in third place in the first round.
- The chart below shows all come-from-behind victories in the U.S. since 2004:
Technical Property in Practice: Condorcet Winners
The Condorcet criterion states that the candidate who would win a one-on-one matchup against every other candidate should win the election. If such a candidate exists, they are known as the “Condorcet winner”. Ranked choice voting does not guarantee that the Condorcet winner will win the election, but it does make it more likely than single-choice plurality or two-round runoff elections.
- We cannot know for sure how often single-choice plurality elections or two-round runoff elections elect Condorcet winners, because we do not know voters’ back-up choices.
- Of the 322 single-winner RCV elections in the United States since 2004 in which we have sufficient ballot data to assess whether the Condorcet winner won the election, 321 elections were won by the Condorcet winner.
- We have identified only one public RCV election in the United States in which the Condorcet candidate lost: Burlington’s 2009 mayoral election. In that election, the three strongest candidates, once all others had been eliminated, had 37%, 34%, and 29% support. The candidate in third place, Andy Montroll was eliminated. However, analysis of ballot image data from the election showed that supporters of the top two candidates had each overwhelmingly ranked Montroll before the other, making him the Condorcet candidate. Whether it would have been better for Montroll to win the election despite attracting so little core support may be disputed, but it is certain that he would have also lost election under a two-round runoff or a single-choice plurality system, reinforcing that RCV elects Condorcet winners more often than either of those systems.
- In the rare situation in which RCV would not elect the Condorcet winner, that necessarily means that the Condorcet winner attracted too little core support to come in either first or second place in the final round.
Technical Property in Practice: Monotonicity
Monotonicity in ranked voting means that ranking a candidate lower can never help them, and ranking a candidate higher can never hurt them. Any voting method in which votes are counted in rounds has the possibility of a non-monotonic outcome, including RCV and two-round runoff elections.
We have not identified any RCV election in which any group of voters has attempted to exploit the possibility of non-monotonicity for strategic purposes. Doing so successfully would both require a highly unusual set of circumstances, and a detailed and accurate understanding of how the electorate will rank the candidates. Because this is prohibitively difficult, the issue of monotonicity under RCV is largely academic - it has never had any impact on any RCV campaign and is unlikely to have any impact in the future. Learn more about monotonicity in our FAQ.
- Out of 353 RCV elections having taken place in the United States as of April, 2020, we have identified one contest with a possibly non-monotonic outcome: the 2009 mayoral race in Burlington, VT.
Whether this election constitutes a non-monotonic outcome depends on how strictly the criterion is defined. There was no candidate that could have won merely by voters ranking him lower. However, if between 367 and 589 Wright voters had instead ranked Kiss first (without changing any other ballots), Wright would have been eliminated instead of Montroll, and Montroll would then beat Kiss. In other words, there is a group of voters that could have caused Kiss to lose by ranking him higher. However, this would be Wright voters helping to elect Montroll. No group of voters could have elected their own preferred candidate by ranking that candidate lower.
