Here are the candidates for the next U.K. leader. Yes, Boris Johnson is one of them

Following the resignation of Liz Truss as Britain's fourth prime minister in a little over six years, her Conservative Party — in power since 2010 — is racing to select a replacement.

Candidates have until Monday to put their name forward, but party officials have announced that in order to be considered they will have to show they have the backing of 100 Conservative legislators, about a third of the party's lawmakers in the House of Commons.

At most, this means there can only be three contenders for the first...