Forms of RCV
Key: SW= single winner, MW = multiple winners
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Voting Method
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SW or MW?
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How It Works
[For SW, the instant runoff is triggered if no majority is achieved in round 1]
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Where It’s Used
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Instant-runoff voting (IRV)
video
[What most people think of when they think of RCV]
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SW
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The lowest vote-getter is eliminated, and each vote for that candidate is transferred to the next-highest-ranked, non-eliminated candidate on the ballot.
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San Francisco, Santa Fe, Maine, New York City and a dozen other places
(Boulder starting in 2023)
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Top-two IRV or contingent vote
[The supplementary vote limits voters to only 2 rankings
video]
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SW
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All but the top 2 vote-getters are eliminated in the first round. Votes for eliminated candidates are transferred to the highest ranked of the 2 remaining candidates on each ballot.
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North Carolina 2010; London, UK
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Top-four plurality primary with an IRV general election
(top-5 primary) video
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SW
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All candidates run against each other in a plurality primary election. The top 4 candidates proceed to an IRV general election. Unlike other IRV versions, this version does not eliminate a second election.
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Alaska starting in 2022.
Political parties are challenging the method because no party is guaranteed to appear on the general election ballot
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Single transferable vote (STV)
video
[a proportional voting method]
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MW
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Candidates who receive the threshold of votes are elected. Any surplus votes are transferred to the next highest ranked of the non-eliminated, non-elected candidates. Lowest vote-getters are eliminated sequentially until all seats are filled.
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Cambridge, MA; Arden, DE Board of Assessors; Eastpointe, MI city council; some members of two boards in Minneapolis
(Boulder 1917-1947)
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15% threshold proportional allocation
video
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MW
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Using an IRV tabulation, the lowest vote-getter is eliminated in each round until all remaining candidates have at least 15% support, whereupon candidate delegates are proportionally allocated.
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2020 Alaska, Hawaii, Kansas and Wyoming Democratic presidential primaries to allocate delegates to the national convention
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Preferential block voting
video
[NOT a proportional form; voters do not have an equal voice in these elections]
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MW
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The first seat is filled using an IRV tabulation. Then all ballots are tabulated again using IRV but ignoring the winning candidate. The process is repeated until all seats are filled.
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Payson, UT; Vineyard, UT; A pilot project allows any Utah municipality to use preferential block voting through the end of 2025
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Bottoms-up RCV
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MW
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Conduct IRV tabulation rounds but stop when the number of non-eliminated candidates equals the target number.
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Allowed under Utah HB 75 for municipal primaries to select general election candidates equal to 2 times the number of seats to fill
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