A man in London holds up a painting in protest of British Prime Minister Theresa May and her cabinet on Friday. May lost her party’s majority in Britain’s election Thursday, but the Conservative leader is resisting calls to step down. (Gerry Penny/European Pressphoto Agency)

Theresa May has been a politician for over two decades, working her way up from local council member to British prime minister. But in a crucial bid to expand her parliamentary majority, the Conservative leader seemed to abandon the first rule of politics — you have to persuade voters to support you.

May led her Conservatives to an electoral drubbing on Thursday, losing the party’s majority in a snap election she had chosen to call. The result was as unexpected as Britain’s decision last year to leave the European Union. 

As was the case with the spectacular fall of David Cameron, her Conservative predecessor who resigned after losing the Brexit vote he had initiated, May’s wound is self-inflicted. She emerges from the election gravely diminished, failing in her objective of strengthening her hand ahead of divorce negotiations with the European Union.

Buoyed by early polls that suggested she would eviscerate the Labour Party led by Jeremy Corbyn, May did not campaign vigorously. She skipped debates and spoke in sound bites when she addressed voters, whom she promised “strong and stable leadership.”

Britain responded by dealing a devastating blow to her leadership. The Conservatives won 319 seats in Parliament, seven shy of a working majority in the 650-member body.

(Sarah Parnass/The Washington Post)

The disappointing result immediately prompted calls for May to step down. Corbyn said early Friday it was time for her “to go.” Tim Farron, leader of the center-left Liberal Democrats, said that “if she has an ounce of self-respect, she will resign.”

Even as many in her own party appeared to rally around her — or at least hold their tongues — some acknowledged that May had stumbled.

Conservative lawmaker Heidi Allen said the Brexit negotiations, which are set to begin in just over a week, could give May a lifeline. But she predicted that the party’s leader would soon be forced out.

“I don’t see any more than six months,” she told a British radio station.

Sarah Wollaston, another Conservative member of Parliament, criticized the election campaign and called for May’s inner circle of advisers to be removed. 

“Hope we never again have such a negative campaign. The public just don’t want US-style attack politics,” she tweeted.

But May resisted calls to step down, saying that she would form a new government by working with the Democratic Unionist Party of Northern Ireland. 

The prime minister’s supporters were left wishing she had remained steadfast in her repeated vows that there would be no early election. But in April, May changed her mind, calling a vote three years before the end of her term.

At first, the idea seemed sensible enough, as opinion surveys suggested she would sail back to Downing Street with a hefty majority. She adopted a hard line on immigration and globalization, arguing that only she was in a position to secure Britain’s future outside Europe.

What was difficult, however, was convincing voters that she stood for anything but staying the course, a future rejected by those hostile to Brexit, hostile to the government’s record of budget cuts or simply hostile to a leader who seemed unwilling to roll up her sleeves and work for her majority. 

One district near her own, in Reading, offered a window into the damage done to the Conservatives. Its incumbent, Rob Wilson, who was in office since 2005 and had been minister for civil society under May, lost his seat to a local Labour council member.

A rail and commercial hub that is home to a major university, Reading revealed that May’s embrace of a severe version of Brexit, designed to win over supporters of the far-right U.K. Independence Party, or UKIP, carried costs.

Simon Round, a 44-year-old Labour voter here, said political moods have shifted as people, many of them young and pro-Europe, have moved south from London to Reading.

“I’m a ‘remain’ voter; I don’t want a hard Brexit,” said Jo Purdey, 46, who has voted for different parties in the past but saw Labour as the main force of opposition to May’s government. 

Conservative voters expected the result, having observed an enthusiasm gap. Dawn Harvey, 49, said Labour signs decorated her neighborhood — mainly, she said, because of “anger about Brexit.”

Wilson said the inclusion of controversial changes to the country’s pension system in the Conservative manifesto cost him the support of older voters, whose support he needed given the large number of left-leaning students in the district.

“I’m sure no one intentionally set out to lose me my seat,” he said, declining to point a finger directly at May, but he said “changes in how her inner circle works” were necessary to ensure broader party consultation on contentious policy.

May’s steep fall stunned Britain, casting doubt on her credibility in negotiations over the terms of Britain’s exit from the E.U.

“A few months ago, Theresa May looked the most authoritative prime minister in more than a decade,” said Matthew Francis, a political historian at the University of Birmingham. “This morning, she looks like the biggest political failure in the Conservative Party’s recent history.”

May’s troubles mounted as the campaign wore on, the 20-point lead she initially enjoyed evaporating. One flash point was a Conservative pledge to rewrite the way elderly people pay for their social care, a centerpiece of the Conservative platform from which May had to backpedal. And following a deadly terrorist attack five days before the vote, she also faced criticism over her six-year tenure as home secretary. Her critics argued that she had been responsible for national defense at a time when the Conservative government oversaw cuts to the police.

Labour’s broadside against austerity struck a chord, particularly with younger voters.

Timothy Heppell, a political scientist at the University of Leeds, said the Conservative campaign was held back by May’s “focus on Brexit and her neglect of other issues that relate to standards of living.” 

Even on Brexit, however, the Conservatives miscalculated, analysts said.

“The Conservatives anticipated that many of those who voted UKIP in 2015 and then for Brexit in 2016 would switch to Conservative, especially in the Labour-held marginals,” said Ron Johnston, an expert on the political geography of Britain at the University of Bristol, referring to districts where the Labour incumbent was vulnerable.

“They got it wrong,” he said. “In the Labour-held marginals, many former UKIP voters went back to Labour rather than switch to the Tories. Brexit didn't matter to them — and many of them, especially the old, were put off the Tories by their policies on social care and pensions.”