As of July 13th, the United Kingdom has its second ever female Prime Minister, Theresa May, following David Cameron’s resignation of the Conservative Party leadership and her subsequent election to the post. After Brexit’s victory in the June referendum, David Cameron announced he would step down by October. Five candidates announced their candidacy for the leadership job: Work and Pensions Secretary Stephen Crabb, Justice Minister Michael Gove, Home Secretary Theresa May, junior Energy and Climate Change Department minister Andrea Leadsom, and former Defence Secretary Liam Fox.
Elections for the Conservative Party’s leader effectively take the form of ranked choice voting (RCV), though they are not explicitly RCV, but rather consist of multiple rounds of voting with the least popular candidate being eliminated each round. Conservative members of the House of Commons (MPs) first narrow down the field to two candidates before a popular vote of all Conservative Party rank-and-file members is held over the span of several weeks. In this case, 329 Conservative MPs (Cameron chose to abstain throughout) voted, with May receiving the support of half. Fox finished last in this first round vote, and was eliminated, endorsing May in the process. Crabb withdrew from the race that same day after finishing second bottom; he also endorsed May. With three candidates remaining for the second-round vote, Michael Gove finished last and was eliminated. This left two candidates, Theresa May and Andrea Leadsom, for the party membership to choose between over the next several weeks. Preliminary plans were that September 9th would be the last day for votes to be cast. Four days later, however, Leadsom unexpectedly withdrew from the race, eliminating the need for the party membership ballot, and May immediately became the new Leader of the Conservative Party.
The Conservative Party adopted this electoral system for its leadership elections in 1998. It was first used in 2001 to elect Iain Duncan Smith, with Smith defeating Kenneth Clarke in the party membership vote. Michael Howard ran unopposed in 2003, so no voting was required, while David Cameron’s 2005 election went to a full party membership vote where he handily defeated David Davis.
Meanwhile, the Labour Party is having a leadership election of its own beginning at the end of August, with former Shadow Foreign Secretary Angela Eagle and former Shadow Work and Pensions Secretary Owen Smith challenging current party leader Jeremy Corbyn for the party’s top post. This election will explicitly use ranked choice voting, though it is referred to as the “Alternative Vote” in the UK. Britain’s third-largest party, the Liberal Democrats has used the Alternative Vote to elect its leader ever since the party’s foundation in 1988. There are two reasons for using this system. First, it allows the parties to go straight to a full party membership vote instead of using a series of MP votes to narrow down the field. And second, it avoids concerns about vote splitting in elections with more than two candidates. In 2014, FairVote's Research Director Sarah John highlighted how common ranked choice voting is for party leadership elections among English-speaking countries.