LONDON _ Britons went to the polls Thursday in a bitterly divisive national election that could help propel the country out of the European Union, prolong a debilitating Brexit impasse, or give a glimmer of hope to those who want to remain part of the 28-nation bloc.
With all 650 seats in Parliament up for grabs, Prime Minister Boris Johnson's Conservative Party was running ahead of Jeremy Corbyn's opposition Labor party, according to opinion polls _ although that lead appeared to narrow in the days before the vote.
The 55-year-old prime minister, whose election mantra was "Get Brexit Done," and his Conservatives need to do more than win a plurality of parliamentary seats. Unless the party achieves 326 parliamentary seats, a majority, Johnson's tenure could be in jeopardy, some analysts said.
"If Conservatives fail to win adequately enough, even if they win more seats than Labor, Boris Johnson may find himself out," John Curtice, a polling expert at the University of Strathclyde in Scotland, told the BBC.
On Wednesday, the final day of the five-week campaign, leaders of all the main political parties made a last dash around the country, knocking on doors and giving stump speeches. On one point all sides agreed: They painted the vote as the most consequential in a generation.
The vote is also considered one of the most volatile in years, with opinion polls conducted in the days before the election suggesting that millions of people remained undecided. Among Britain's population of 66 million, 46 million are eligible to vote, including many young people who have reached voting age since the Brexit referendum more than three years ago.
Many voters were setting aside longtime party loyalties to express their Brexit views, leading to a rise in so-called tactical voting, meant primarily to blunt the power of the opposing side.
"The actual number of people saying they are going to vote 'tactically' has shot up in the last few weeks," said Jess Garland, director of policy and research for the Electoral Reform Society, an independent voting-rights and campaign watchdog group. She said research suggested that about 30% of the electorate intended to vote "to keep out the one they least like."
Johnson sought to rally voters exhausted by wrangling that erupted after the June 2016 Brexit referendum, when voters narrowly decided, 52% to 48%, to leave the bloc. The infighting since then has toppled two prime ministers and divided families and communities.
In an effort to break the deadlock, the election was called nearly two years ahead of schedule.
"A great future is there within our grasp, but I need your vote," the prime minister told a campaign rally in central England on Wednesday. "Even if you have never voted Conservative before, this is your chance to be heard, and I promise I will not let you down."
Corbyn, meanwhile, zigzagged north to Scotland and south to London, making last-minute appeals in key constituencies. The 70-year-old party leader said a Labor ballot was a "vote for hope" after nine years of Conservative-imposed austerity, and called on voters to "elect a government that they can trust."
Labor's Brexit stance is ambiguous. Corbyn said he would renegotiate a divorce deal with the EU, and then put the vote to the public in a second referendum. But he did not publicly take sides as to whether Britain should stay or go.
The party sought instead to highlight social issues, promising heavy investment in the struggling National Health Service, together with schools, housing and transport. The NHS, the country's universal healthcare system, became an election tinderbox, with Labor warning that Brexit could leave it in peril of predatory U.S. health companies. Johnson denied that.
The election is unusual in that both Johnson and Corbyn have negative personal-approval ratings, meaning the result could hinge on which of them proves the least unpopular.
Voters have trust issues with Johnson, who is widely known as being casual with the truth. He dodged high-profile interviews with broadcasters during the campaign and was accused of lacking empathy after refusing to look at an image of a sick 4-year-old boy lying on the floor in an overstretched hospital emergency department.
Corbyn has his own hurdles to overcome. He has been dogged by a persistent strain of anti-Semitism within his party, which led Britain's chief rabbi, Ephraim Mirvis, to declare he was unfit for office.
Anti-Brexit votes are scattered among several parties, with some in the Labor ranks, but also in pro-European parties such as the centrist Liberal Democrats, nationalist parties in Scotland and Wales, and the environmental-minded Greens.
Johnson has pledged that armed with a majority, he would get Parliament to swiftly ratify his renegotiated withdrawal accord and preside over a split with the EU on Jan. 31. But critics call his "Get Brexit Done" slogan misleading at best; that deal covers only the divorce terms and would mark the start of drawn-out, difficult negotiations on future trade relations with the bloc.
The polls opened at 7 a.m. Thursday and close at 10 p.m. Exit polls were to be broadcast soon after the voting ends, giving an indication of the likely outcome, with most results known early Friday.
It was Britain's first December general election in nearly a century. Generally all parties try to avoid balloting at this time of year because of early darkness and blustery cold.
(Special correspondent Boyle reported from London and Times staff writer King from Washington.)
