For Donald Trump in the U.S., read Boris Johnson in the U.K. The former mayor of London, who was born in Manhattan when his father was studying economics at Columbia University, has long harbored ambitions of succeeding David Cameron as Prime Minister — and after his old schoolfriend’s resignation Friday morning, he might now get the chance.

Over the next three months, the Conservatives’ 330 MPs will whittle down the leadership candidates down to two, when the party’s estimated 150,000 membership will decide who will lead a country of 64.1m people until the 2020 general election. MPs will feel obliged to make sure Johnson is one of those two, Conservative lawmakers acknowledge, because that membership would “go ballistic” if they didn’t get a chance to vote for the great entertainer of British politics.

Johnson, the U.K.’s most popular politician, gambled big by opposing Cameron over Britain’s European Union in/out referendum, despite belonging to the same Conservative Party (and having known Cameron since the two were at prestigious Eton College). But it was Johnson who quickly became the poster boy of the race, while the Prime Minister struggled to persuade the electorate that leaving the E.U. would badly damage the UK’s economy.

In the end, the bet paid off. In defiance of bookmakers, 52% of the country put their ‘x’ in the Leave box of their ballot papers on June 23; despondent Remain proponents left their end of campaign party early.

Cameron immediately announced his intention to resign, but will stay in office until his successor is elected by the Conservatives ahead of their annual party conference in October. Johnson described his longtime rival as “brave and principled” this morning, but is now a huge favourite to take his job and home at No 10 Downing Street. He is expected to spend the weekend setting up his campaign team.

The former Mayor is a well-known wit who once described the likelihood of his becoming Prime Minister as “about as good as the chances of finding Elvis [Presley] on Mars or my being reincarnated as an olive.” But this morning he struck a more sombre, statesmanlike tone, insisting that leaving the E.U. does not mean isolationism: “We cannot turn our backs on Europe, we are part of Europe.”

The party is hardly united behind Johnson, though. Many MPs who backed Cameron over the E.U. are wounded by the result after what was a particularly vicious campaign and want to rally behind a ‘Stop Boris’ candidate. A source close to Johnson told TIME they are keeping an eye on Mark Harper, the well-liked chief whip who is nevertheless a virtual unknown outside of Parliament. A member of the Opposition Labour Party says he would “fear” Harper’s keen intelligence if he somehow made the final two and beat Johnson.

Most likely is Theresa May, the Home Secretary. Although she supported Cameron over the E.U., May is a long-standing Euroskeptic whose public backing for the campaign was widely perceived as lukewarm at best. A prominent Brexiteer says: “If you look at the last Labour government, they changed Home Secretaries more often than they changed their underpants. May has been Home Secretary for six years … It’s going to be Boris plus another person and that other person could be May.”

The biggest casualty of the Remain campaign was Chancellor of the Exchequer George Osborne, a close friend of Cameron who was for a long time considered the favourite to succeed him. Osborne warned that Brexit would result in £30bn of spending cuts and tax rises, which Conservative Brexiteers immediately dismissed as a “punishment” that they would oppose when brought to Parliament. A calculated politician who was previously considered a master electoral tactician, Osborne will have worked out that he cannot now command sufficient support among MPs and likely will not stand.

Johnson could also face a challenge from fellow Brexiteers, but the man he would fear most, Lord Chancellor Michael Gove, is unlikely to stand. Both publicly and privately Gove, who is credited with giving the Brexit campaign an intellectual backbone, has been emphatic that he has no ambition to be Prime Minister.

More probable are energy minister Andrea Leadsom and Chris Grayling, a cabinet member who has so far refused to rule out a leadership tilt. Although Leadsom had a strong Brexit campaign with her calm, authoritative manner playing well in television debates, neither are likely to get the MPs they need to make the run-off. The point of a Grayling candidacy, it is thought, would be to make sure he is in the frame to get a big job afterwards.

The oddmakers say it’s Johnson versus May. They were badly wrong over the E.U. referendum, but with Cameron’s resignation still fresh it seems unlikely that they are making a second mistake.

This article was originally published on Time.com.