Can ranking a candidate higher on your ballot make them lose?
In a 2009 mayoral race in Burlington, Vermont, 54% of voters ranked one candidate above the winner, who got there thanks to 750 ballots that ranked him last.
▶ Start the storyIn some ranked voting systems it can, although rarely. The system in question is instant-runoff voting (IRV), known in the United States as ranked-choice voting. Each voter ranks the candidates. In each round, the candidate with the fewest first-preference votes among the remaining candidates is eliminated, and each eliminated candidate's ballots move to the next-highest preference on them, until only one candidate is left.
Step 1: Voters rank the candidates
Step 2: The fewest first choices is eliminated
Among the remaining candidates
Step 3: Their ballots move on
To the next-highest preference on each ballot
Step 4: Repeat until one is left
Social choice theorists test a voting rule with the monotonicity criterion: a voter ranking a candidate higher on their ballot should not cause that candidate to lose, and a voter ranking a candidate lower should not help that candidate win. Negative responsiveness occurs in instant-runoff voting, the single transferable vote, and the two-round system.
A notable case came in the 2009 mayoral election in Burlington, Vermont, where Bob Kiss won as a result of 750 ballots ranking him in last place. Although 54 percent of voters ranked Andy Montroll above Kiss, Montroll was defeated as a result of a first-round spoiler effect. Later analyses stated that Kurt Wright acted as a spoiler by pulling moderate votes from Montroll, who would have defeated Kiss in a one-on-one race.
750
The city had approved IRV with a 64% vote in 2005. In March 2010 a citizen's initiative repealed it by 52% to 48%.
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Recap
A fair-looking elimination count can respond backwards to votes, so ranking a candidate higher can, rarely, make them lose.
💡 A trick to remember it · Think of a seesaw that can, rarely, tip backwards: add weight on your side and, now and then, it goes up instead of down.
Surprising fact · In Burlington in 2009, Bob Kiss won as a result of 750 ballots ranking him last, though 54% preferred Andy Montroll to him.
Sources (3)
No source, no claim. Every fact in this lesson (23 claims) cites at least one of these.