Preferential Voting

Preferential voting is an umbrella term for electoral systems in which voters rank candidates in order of preference rather than selecting only one. If no candidate secures the required threshold (usually a majority) on first preferences, lower-ranked choices are progressively counted to determine a winner.

The most common variants include:

• Instant-runoff voting (IRV), also called the alternative vote, used for Australia's House of Representatives since 1918 and for the Irish presidency. The lowest-polling candidate is eliminated each round and their ballots redistributed to the next-preferred surviving candidate until one passes 50%.
• The single transferable vote (STV), a proportional variant used for the Australian Senate, Irish Dáil, Maltese parliament, and Scottish local councils. Voters rank candidates in multi-member districts and surplus votes above a quota (typically the Droop quota) are transferred.
• Contingent vote and supplementary vote, simplified forms once used for the London mayoral election (1999–2021) before being replaced by first-past-the-post.

Proponents argue preferential systems reduce wasted votes, discourage tactical "lesser-evil" voting, and incentivise broader campaigning since candidates court second preferences. Critics point to higher ballot complexity, slower counts, and—in IRV specifically—non-monotonicity, where ranking a candidate higher can paradoxically cause them to lose (a phenomenon demonstrated in the 2009 Burlington, Vermont mayoral election).

Adoption is uneven. Australia is the largest national user. In the United States, Maine became the first state to use IRV for federal elections (2018), followed by Alaska (2022). New York City adopted IRV for municipal primaries in 2021. The UK rejected the alternative vote in a 2011 national referendum by roughly 68% to 32%.

In Model UN and parliamentary contexts, preferential voting occasionally appears in elections for officers or in straw polls, though most UN bodies use plurality or two-thirds majority rules rather than ranked methods. The Academy Awards' Best Picture category has used a preferential ballot since 2009.