Brexit proponent Boris Johnson will replace outgoing Theresa May as the new British prime minister after winning the leadership of the Conservative Party on Tuesday.
His convincing victory catapults the United Kingdom toward a showdown with the EU and toward a constitutional crisis at home, as British lawmakers have vowed to bring down any government that tries to leave the bloc without a divorce deal.
Johnson, the face of the 2016 Brexit referendum, won the votes of 92,153 members of the Conservative party, almost twice the 46,656 won by his rival, Foreign Secretary Jeremy Hunt.
May will leave office on Wednesday after going to Buckingham Palace to see Queen Elizabeth, who will formally appoint Johnson before he enters Downing Street.
"We are going to get Brexit done on Oct. 31, and we are going to take advantage of all the opportunities it will bring in a new spirit of 'can do,'" Johnson, 55, said after the result was announced.
"Like some slumbering giant, we are going to rise and ping off the guy-ropes of self-doubt and negativity."
Johnson said the mantra of his leadership campaign had been to "deliver Brexit, unite the country and defeat (opposition Labour leader) Jeremy Corbyn — and that is what we are going to do."
Within half an hour of his victory, US President Donald Trump had tweeted his congratulations, adding: "He will be great!".
The men have recently been complimentary about each other — yet Trump is one of the many world leaders, including Russian President Vladimir Putin and Turkish President Tayyip Erdoğan, about whom Johnson has previously made derogatory remarks. In 2015, he accused Trump, then a candidate for office, of "stupefying ignorance" that made him unfit to be president.
The victory for one of Britain's most flamboyant politicians places an avowed Brexit supporter in charge of the government for the first time since the United Kingdom voted to leave the EU in the shock 2016 referendum.
But Johnson — known for his ambition, untidy blond hair, flowery oratory and cursory command of policy detail — takes office at one of the most tumultuous junctures in post-World War II British history.
The pound has fallen sharply in recent weeks on fears of a no-deal Brexit, and stands near $1.24, around its lowest level for two years. With Johnson's win already priced in, it was little changed on Tuesday.
The 2016 Brexit referendum showed a United Kingdom divided about much more than the European Union, and has fueled soul-searching about everything from regional secession and immigration to capitalism, the legacy of empire and modern Britishness.
Brexit, which has already toppled two Conservative prime ministers, will dominate.
Johnson has pledged to negotiate a new Brexit divorce deal with the EU to secure a smooth transition out of the EU before Oct. 31. But if the bloc refuses, as it insists it will, he has promised to leave anyway — "do or die" — on the current agreed date of Oct. 31 — Halloween.
It is a step that many investors and economists say would send shock waves through world markets and tip the world's fifth largest economy into recession or even chaos.
The EU said a no-deal Brexit would be a tragedy for both parties but again said the withdrawal deal was not up for negotiation.
"We look forward to working constructively with PM Johnson when he takes office, to facilitate the ratification of the withdrawal agreement and achieve an orderly Brexit," tweeted the bloc's negotiator, Michel Barnier.
A Brexit without a divorce deal would also weaken London's position as the pre-eminent international financial center while jolting the northern European economy.
Johnson's Conservatives have no majority in parliament and need the support of 10 lawmakers from Northern Ireland's Brexit-backing Democratic Unionist Party to govern.
Even then, the majority is wafer-thin — and some lawmakers have threatened to bring down the government, a step that would probably deepen Britain's political crisis and lead to an election.
The rise of Alexander Boris de Pfeffel Johnson, often referred to as simply "Boris," to the top of British politics is the grandest twist so far in a career that has taken him from journalism via TV-show fame, comedy and scandal into the political brinkmanship of Britain's Brexit crisis.
Born in New York, Johnson was educated at Eton, Britain's most exclusive school, and at Balliol College, Oxford. He began his career at a management consultancy in the City of London but dropped out after a week.
He then turned to journalism, but was sacked from the Times newspaper for making up quotes.
Hired by the Daily Telegraph, Johnson infuriated European officials and delighted then-prime minister Margaret Thatcher by lampooning the European Economic Community with a host of sometimes misleading reports from Brussels.
After entering politics, he was sacked from the Conservative Party's policy team while in opposition for lying about an extramarital affair. He and his wife announced last year they were to divorce and he is currently in a relationship with the party's former communications chief, Carrie Symonds.
But his sometimes shambolic personal appearance and disarmingly self-deprecating persona have allowed him to survive both gaffes and scandal. He served two terms as London mayor, from 2008 to 2016.
His embrace of a court jester role has won over many Britons, fed up of what many see as an out-of-touch political establishment too centered on a London elite. But critics say he lacks the gravitas the job requires.
"He has shown time and time again that he isn't fit to be the prime minister of our country," Jo Swinson, leader of the pro-EU Liberal Democrat party.
In 2016, Johnson became one of the most recognizable faces of the Brexit campaign, which won the referendum by 52% to 48%, but faced accusations of making misleading claims to win support, most notably by stating that Britain would be 350 million pounds ($440 million) a week better off outside the EU.
"I know that there will be people around the place who will question the wisdom of your decision, and there may be some people here who still wonder what they have done," Johnson told party members after his victory was announced.
"I will just point out to you that no one party, no party has a monopoly of wisdom."
By Guy Faulconbridge and Elizabeth Piper/Reuters
Additional reporting by Kylie MacLellan, William James, Kate Holton, Andrew MacAskill, Alistair Smout and Michael Holden; Writing by Guy Faulconbridge; Editing by Kevin Liffey.