What is the alternative vote?

The alternative vote, or AV, is a preferential voting system for single-member seats. Voters rank candidates in order. If no one gets over 50% of first preferences, the last-placed candidate is eliminated and their votes move to the next choice. This repeats until one candidate has a majority. UK voters rejected AV in 2011.

AV keeps one MP per constituency, like first past the post. The difference is that the winner must have majority support once preferences are counted. It is not a proportional system. A party with broad support across the country can still win far more seats than its vote share. It mainly helps candidates who are many voters' second choice. Results can still be lopsided.

In May 2011 the UK held a referendum on replacing first past the post with AV for Westminster elections. It was part of the coalition agreement between the Conservatives and Liberal Democrats. Voters rejected it by about 68% to 32%. Turnout was around 42%. The result settled the issue for a generation, though campaigners now mostly push for fully proportional systems.

AV is used for elections to the Australian House of Representatives. In the UK, preferential ballots like AV are used in some party leadership contests, including Labour's. Supporters say it lets people vote for their real first choice without wasting their vote. Critics say it is complicated and can reward the least disliked candidate. Australian voters must rank every candidate in most cases.