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.

Harrow, J. & Shi, V. 2019. The magic of majority rule in elections. The Hill.

https://e.infogram.com/f4ff3f81-be7b-46c2-8b40-fa5850fdaeef?src=embed2018 Plurality Winsnoborder:none;allowfullscreen5507460

 

RCV and Incumbents

FairVote California. October 2017. RCV and Incumbency in the Bay Area.

 

Come-From-Behind Winners


 

 

 

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.

 

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.

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 by ranking Wright lower. No group of voters could have elected their own preferred candidate by ranking that candidate lower.

 

 

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