British Prime Minister Theresa May shocked her country Tuesday with an unexpected call for June elections, a gamble aimed at increasing her political power at home and enhancing her leverage in Brussels for the high-wire Brexit negotiations.

The move amounted to an ambush of Britain’s weak and fractious opposition, giving them just seven weeks to prepare for a vote that had not been due for three more years.

Brexit brought May to power; her predecessor, David Cameron, resigned after the humbling defeat of his pro-European Union side in last June’s referendum on whether to leave the trading bloc.

If May emerges strengthened from the snap election — as opinion polls currently suggest — she will have greater clout as Britain goes into the complex talks with the remaining 27 E.U. nations, which appear in no mood to offer generous farewell concessions to Britain.

[Theresa May’s element of surprise]

(The Washington Post)

But if anti-Brexit voices do well in the polls, May could be forced to soften her demands that Europe provide favorable conditions for the split.

No matter how the vote swings, the election campaign is certain to reopen some of the wounds from last year’s referendum, as voters are once again asked to consider what kind of future they envision for Britain after its E.U. break.

“I have concluded the only way to guarantee certainty and stability for the years ahead is to hold this election and seek your support for the decisions I have to make,” said May, who last month submitted Britain’s formal request to begin E.U. exit negotiations.

[Britain’s snap elections won’t reverse Brexit. Here’s why.]

May has consolidated power within the Conservative Party. But the lack of her own popular mandate has threatened to become a liability as Britain begins to reckon with the inevitable trade-offs that will come with the Brexit talks.

In the election announcement, May argued that her political opponents — from the independence-minded Scots to pro-E.U. factions in Parliament — are undermining Britain’s negotiating position with the European Union. At the same time, some hard-liners in her own Conservative Party are calling for a “dirty Brexit,” in which Britain could walk away from the negotiating table without any deals with the European Union.

May is also sensing political opportunity.

Her Conservative Party has a narrow majority in Parliament but has opened up a 20-point lead over the opposition Labour Party in recent polls. While May had promised not to call an early election, her allies have been pushing her to break that vow.

[The Brexit road map]

The Labour Party has been at war with itself since the far-left Jeremy Corbyn became leader in September 2015. A recent poll showed that, in a head-to-head matchup between May and Corbyn, not even a majority of Labour voters would want Corbyn as their prime minister.

Corbyn, however, welcomed the snap election as giving “the British people the chance to vote for a government that will put the interests of the majority first.”

[‘Not another one!’ Vote-weary Britons greet election news. ]

Other parties are similarly weakened. The far-right U.K. Independence Party has lost its charismatic leader, Nigel Farage, while its central message — that Britain needs to get out of the E.U. — has been co-opted by May. The centrist Liberal Democrats were all but wiped out in the 2015 election, though they will hope to rally the Brexit referendum’s “remain” voters around their unapologetically pro-Europe stance.

May planned to seek Parliament’s backing Wednesday for the June 8 election.

“We need a general election, and we need one now,” May said, “because we have at this moment a one-off chance to get this done while the European Union agrees its negotiating position and before the detailed talks begin.”

One reason so many were stunned by the move is that May had repeatedly ruled out an early election, and she has staked her reputation on doing what she says. The next election was scheduled for 2020.

May said that she had “recently and reluctantly” decided that a snap election was the only way to guarantee stability and to stop the “game-playing” in Westminster. She cited several examples of what she called “division” in Parliament, including the Labour Party’s threat to vote against the final deal negotiated with the European Union.

[In ‘Brexit capital,’ Labour’s struggles on display]

Tim Farron, leader of the pro-Europe Liberal Democrat Party, said the election offered an opportunity to urge May to take a more conciliatory line in the E.U. talks.

Some critics worry that Britain could lose important trade and other links to Europe by pushing for what May has called a full break from the E.U. There are also concerns over the estimated 3 million E.U. citizens working and living in Britain and the more than 1 million Britons residing across Europe. May said she would seek to preserve their rights.

“If you want to avoid a disastrous ‘hard Brexit.’ If you want to keep Britain in the single market. If you want a Britain that is open, tolerant and united, this is your chance. Only the Liberal Democrats can prevent a Conservative majority,” Farron said in a statement.

The E.U. bureaucracy, however, has shown little interest in giving Britain an easy landing as it seeks to leave the bloc. E.U. officials are still smarting from Britain’s vote and worried that generous concessions could encourage other E.U. breakaway bids around Europe.

European Council President Donald Tusk, a powerful voice in the Brexit talks, summed up the surprise many in Europe felt at May’s announcement. “It was Hitchcock who directed Brexit: first an earthquake and the tension rises,” Tusk wrote on Twitter.

Although Britain as a whole voted 52 to 48 percent in favor of leaving the European Union, majorities in both Scotland and Northern Ireland favored staying.

Scottish leader Nicola Sturgeon has charged that Scotland’s voters are being taken out of the bloc against their will. And she said last month that she wants a referendum on independence — a rerun of a September 2014 vote, in which a majority of Scottish voters opted to stay in the United Kingdom — between the autumn of 2018 and the spring of 2019.

May has repeatedly said that “now is not the time” for a Scottish vote. But she has not threatened to veto another referendum.

Moments after Tuesday’s election call, Sturgeon described it as an attempt by May to move the Conservative Party to the right and “force through a hard Brexit and impose deeper cuts.”

“Let’s stand up for Scotland,” Sturgeon wrote on Twitter.

Witte reported from Paris and Murphy from Washington. Michael Birnbaum in Brussels contributed to this report.

Read more:

As Brexit reshapes Britain, it does the same to Europe

In Shakespeare’s home town, a house divided

Cue the British nostalgia

Today’s coverage from Post correspondents around the world

Like Washington Post World on Facebook and stay updated on foreign news