IRV

Instant Runoff Voting (IRV), also known as ranked-choice voting in its single-winner form, is a voting system in which voters rank candidates in order of preference. It is used for single-winner elections rather than proportional representation.

In an IRV election, ballots are counted in rounds. In the first round, only voters’ first preferences are tallied. If a candidate receives a majority of the active votes, that candidate wins. If no candidate achieves a majority, the candidate with the fewest votes is eliminated, and ballots for that candidate are redistributed to the next preferred candidate still in contention. This process repeats until a candidate secures a majority of active votes or until only one candidate remains. Some ballots may become exhausted if voters do not indicate a remaining preference.

IRV has been adopted in various contexts worldwide and is often described as a form of ranked-choice voting, which also encompasses methods like multi-winner STV. In practice, IRV is used for single-seat elections in many cities and jurisdictions, and several regions have adopted ranked-choice voting for broader elections, including some U.S. states and national-level contests in other countries. The specific counting rules, such as how exhausted ballots are treated and how the majority is defined, can vary by jurisdiction.

Advantages cited for IRV include reducing the spoiler effect, encouraging voters to express preferences without fear of wasting ballots, and increasing the likelihood that the winner has broad support among voters. Criticisms include ballot exhaustion, greater counting complexity, and the possibility of non-monotonic outcomes or strategic ranking in some situations. Proponents argue that IRV can produce more representative outcomes, especially in races with multiple credible candidates.