LONDON — Only one person, the joke doing the rounds in Parliament goes, can stop the disheveled, blond-haired, crowd-pleasing former foreign secretary, Boris Johnson, from becoming the country’s next prime minister.

That is Mr. Johnson himself.

One of Britain’s most recognizable, and now most divisive politicians, Mr. Johnson has a history of verbal gaffes, a poor record as a minister and many enemies in Parliament, not to mention among the voters who reject Brexit, which he helped persuade Britons to embrace in a 2016 referendum.

But his charisma, flair for publicity and record of winning two elections as mayor of London make him the runaway favorite in a crowded field to succeed Prime Minister Theresa May, according to bookmakers.

A victory for Mr. Johnson would have significant repercussions and could increase the prospects of Britain hurtling out of the European Union without an agreement at the end of October, despite the potentially dire economic consequences.