LONDON — The day after a historically decisive election in Britain, Prime Minister Boris Johnson vowed to unify a divided country, while leaders of the opposition Labour Party fought over the reasons for their crushing loss.

On Friday morning, Johnson had an "audience" with Queen Elizabeth II at Buckingham Palace, where, in keeping with tradition, he asked for her permission to form a government. In the final tally, his party won 365 out of 650 seats in the House of Commons.

“Let the healing begin,” Johnson urged to a society that has been at war with itself since a narrowly decided Brexit referendum more than three years ago.

He vowed to use his party’s commanding parliamentary majority — the largest the Conservatives have enjoyed since the times of Margaret Thatcher — to make Brexit happen but also “to unite and level up.”

Unity may prove an elusive mission, especially since Scottish voters flocked to a nationalist and pro-Europe party that immediately threatened to pursue a second independence referendum.

Even if many Brits were exhausted by the Brexit debate, polls suggest they are as divided as ever on their country’s relationship with the European Union.

The prime minister said, essentially, that resistance is futile and that Britons who hoped to remain in the E.U. must move on.

Punching the air, in a rumpled suit and with his blond mop of hair askew, Johnson proclaimed: "Getting Brexit done is now the irrefutable, irresistible, unarguable decision of the British people."

"With this election, I think we've now put an end to all those miserable threats of a second referendum," he said.

Later in the day, he addressed those partial to the E.U. in gentler terms.

“We in this one-nation Conservative government will never ignore your good and positive feelings of warmth and sympathy towards the other nations of Europe,” Johnson said while speaking outside Downing Street. “Because now is the moment — precisely as we leave the E.U. — to let those natural feelings find renewed expression in building a new partnership, which is one of the great projects for next year.”

Johnson wants to get Britain out of the E.U. by the end of next month and to have a new trade deal with Europe in place by the end of an 11-month transition period. Now that he has a parliamentary majority, that first part should be relatively easy. The second part remains hard.

A lingering question was how much Johnson would pivot away from the austerity politics imposed after the financial crisis by previous Conservative governments to embrace a kind of Tory nanny state.

He made big spending promises in the campaign: spending on nurses, hospitals, schools and police. On Friday, he told traditional Labour voters who supported the Conservatives for the first time that he would work to prove they made the right choice.

As significant as Johnson’s victory was the defeat for the Labour Party of Jeremy Corbyn and his self-described radical socialist agenda.

Labour on Thursday had its worst electoral showing since World War II.

Conservatives won big by taking a battering ram to Labour's "red wall," the line of fading industrial towns in England's north and Midlands, where the working classes have traditionally backed Labour since World War I.

On Friday, Corbyn announced that he would not lead the party in any future general elections, though he hoped to stay on as leader during a period of "reflection."

When Corbyn became party leader in 2015, his supporters believed his left-wing populism was the answer to the rise of the populist far right. Liberal politicians beyond Britain — U.S. Sen. Bernie Sanders (I-Vt.) among them — were urged to take heart from the way he succeeded in shifting his party left.

Hours before the polls closed in Britain on Thursday, Rep. Alexandria Ocasio-Cortez (D-N.Y.) sought to rally support for Labour.

“The hoarding of wealth by the few is coming at the cost of peoples’ lives,” she tweeted. “The only way we change is with a massive surge of new voters at the polls. UK, Vote!”

But on Friday, the vote result was seen in some quarters as a potential warning light about the viability of left-wing platforms in Europe — and maybe in the United States ahead of a presidential election.

“The lessons are ones you’d expect to draw: It’s really easy to appeal to your base — bases are really easy to speak to because they are there,” said Simon Usherwood, a politics professor at the University of Surrey.

What’s hard, Usherwood said, “is reaching out to people in the center, the swing voters,” which is important in countries like the United States and Britain, both of which have two dominant parties. “If you don’t reach out and try and take people off the other lot, you’re not going to get anywhere.”

The arguments that raged within Labour on Friday mirrored arguments that have divided left-wing parties across the Western world, though Brexit complicated matters.

Corbyn and others blamed the party’s losses primarily on the dominance of Brexit.

“Brexit has polarized and divided debate within this country,” Corbyn said Friday morning. “It has overridden so much of a normal political debate.”

While Johnson led the crusade for Brexit, Corbyn took a noncommittal stance, giving lukewarm support to the idea of a second referendum and saying he would remain neutral in that vote.

Ian Lavery, the Labour chairman, blamed the party’s poor showing on the promise of a second referendum. “Ignore democracy and, to be quite honest, the consequences will come back and bite you,” he told the BBC.

Others pointed the finger at Corbyn, a leader who is highly unpopular with the British public and who struggled to address allegations of anti-Semitism within his faction.

“Corbyn was a disaster on the doorstep,” senior Labour politician Alan Johnson said in an apoplectic exchange on television with a Corbyn acolyte. “Everyone knew that he couldn’t lead the working class out of a paper bag.”

At times, Corbyn’s supporters seemed to be campaigning more against centrists than they were against Johnson and the Conservatives.

Labour, with the support of activists in the far-left Momentum movement, purged the party of centrists, whom they branded as revanchist disciples of former Labour prime minister Tony Blair. Blair is loathed by many Labour activists today, largely for his support of the Iraq War and his “third-way” neoliberal economic policies that echoed those of President Bill Clinton. But Blair was also the most electorally successful, longest-serving Labour prime minister of the postwar years.

Labour’s debate about purity vs. pragmatism is one that should be familiar to the American left.

But even beyond Brexit, there are reasons to be cautious about extrapolating to an American context.

What counts as liberal in the United States would hardly qualify as such in Britain, a creator of the postwar welfare state. By British standards, figures like Elizabeth Warren, seen as liberal in the United States, are more in line with traditional mainstream Labour figures, at least in terms of their policy proposals.

But Britain, much like the United States, has also traditionally shied away from left-wing leaders with policies as far to the left as Corbyn’s. Even in the 1960s and 1970s, Labour Prime Minister Harold Wilson was relatively moderate by the standards of the time, as was James Callaghan after him.

Labour has traditionally been strong on defense, anti-Communist and relatively low on ideology. A Corbyn victory would have represented a radical departure.