Boris Johnson, the former foreign secretary, is a front-runner, but he divides opinion. He flopped in his previous role, but he has star quality and is seen as capable of winning back party supporters. Mr. Johnson, like other contenders, wants to keep open the option of a no-deal Brexit.

Next: The contest will be fought among 313 Conservative lawmakers, who will narrow the field to two candidates in a series of ballots. The final choice will then be made by about 150,000 members of the Conservative Party by the end of July.

Drugs issue: While you might think Brexit would be the key issue, what has dominated part of the contest is the revelation that the environment secretary, Michael Gove, used cocaine a couple of decades ago. (Other candidates have admitted past drug use.)