Boris Johnson, former U.K. foreign secretary, delivers a speech during the Conservative Party annual conference in Birmingham, U.K. (Photographer: Chris Ratcliffe/Bloomberg)

Boris Johnson Pitches for Leadership With Pledge of Brexit on Oct. 31

(Bloomberg) -- Boris Johnson will launch his campaign to become U.K. prime minister Wednesday morning with a promise to get Britain out of the European Union on Oct. 31, come what may.