Liz Truss or Rishi Sunak will be the next Prime Minister of the UK

Rishi Sunak and Liz Truss are through to a final round of voting in the UK, where the Conservative Party is picking a new leader—and in effect a new Prime Minister—following the resignation of Boris Johnson.

In the penultimate round of votes, cast by sitting Conservative MPs, there wasn't much between the top three candidates, with former finance minister Sunak receiving 137 votes, foreign secretary Truss receiving 115 votes, and Penny Mordaunt eliminated with 105 votes.

Though Sunak is most popular among Conservative MPs, party rank-and-file vote in the last round, and Truss is overwhelmingly preferred by them. Support for Mordaunt, the bookies' early favorite, subsided after a weekend of attacks from conservative media infuriated by her past support for transgender rights.

In the United Kingdom, by convention, the leader of the majority party (or the largest party in a majority coalition) forms a government and serves as Prime Minister. When a sitting Prime Minister steps down as party leader, but does not call a general election, this results in the somewhat undemocratic spectacle of a political party getting to pick a new Prime Minister.

Although Mr Sunak has come first in all the voting rounds among Tory MPs, surveys have suggested he may struggle to maintain his advantage among members.

A YouGov survey of 725 party members on Monday and Tuesday suggested Mr Sunak would lose to either Ms Mordaunt or Ms Truss in a head-to-head.

The poll had Ms Mordaunt beating Mr Sunak by 51% to 37% and Ms Truss

This is an interesting race in the sense that the worse the winner, the better it might be for the opposition Labour party, which did not want to face the relatively moderate and appealing Mordaunt. But that impulse is familiar ground for the American center-left, and it didn't work out for them.