Exit polls and partial results after a nationwide vote to pick Britain’s next Parliament showed the Conservative Party with a surprisingly commanding lead Friday, just short of a majority and in a strong position to return to power.

The projections defied virtually all pre-election polls, which forecast a virtual tie between the Tories and the opposition ­Labor Party in the popular vote. Both main parties had been expected to fall well short of the majority needed to claim power outright.

But as the counting continued into dawn Friday, all signs pointed to an emphatic margin in favor of the Conservatives and their leader, Prime Minister ­David Cameron, and to a major disappointment for ­Labor as well as the Liberal Democrats, who paid a steep price for having entered into a coalition with the Conservatives for the past five years.

At dawn Friday, Labor leader Ed Miliband delivered what amounted to a concession speech, saying it had been “a very disappointing and difficult night” for his party.

Meanwhile, in the election’s other stunning development, though one that had been predicted, the Scottish National Party (SNP) was redrawing the map of Scotland with what looked like a historic rout in what has long been one of Labor's most reliable strongholds.

Britain's 2015 election is one of the tightest in decades and could lead to potential government gridlock. The Post's Adam Taylor explains the possible outcomes, depending on which parties win the most seats in parliament. (Alice Li/The Washington Post)

The exit poll released by the BBC just after the polls closed predicted that the Conservatives would win 316 seats in the 650-member Parliament, compared with just 239 for Labor. The results shocked most political analysts, and party leaders greeted the numbers with considerable caution, if not outright ­disdain.

But as one after another of the individual races reported results, there was growing acceptance that the exit polls had caught the mood of the voters far better than had the pre-election polls.

Even in winning 316 seats, the Conservatives would still be short of a majority and would need the support of others to govern. But they were expected to emerge in a far stronger position to begin to form a new government than had been ­predicted.

Another Conservative-led ­government likely would mean doubling down on austerity for the British economy after years of belt-tightening, as well as a potentially divisive debate over Britain’s membership in the European Union. With the rise of the SNP, the results also presaged increased tensions between England and Scotland and renewed calls for Scottish independence.

Leading Tories, as the Conservatives are known, cautiously declared victory late Thursday, saying their record in bringing the economy back from the depths of recession had been validated. ­Labor Party leaders, meanwhile, attempted to put the best face on what looked to be a deeply disappointing result.

Such a wide Tory margin would leave Labor in an extremely difficult position. Miliband, who had won plaudits for his conduct during the campaign, had hoped to be able to form a minority government, even if it came in second in total seats, by relying on the votes of the SNP and possibly others.

But with Labor running poorly, Miliband was already facing questions about whether he can continue as the leader of the party given the results. In a short speech, he called on the next government to “keep our country together,” noting the surge of nationalist sentiment in Scotland.

British Prime Minister David Cameron's Conservatives are on course to win the most seats in Parliament according to exit poll, but not an outright majority. (Reuters)

The counting continued into the early morning hours Friday, with final numbers not likely to be tabulated until midday. But it was clear that the election had caught even some Conservative leaders by surprise.

Leading Tory politician ­Michael Gove said that if the exit poll results hold, they mean the Conservatives “have won.”

“If­­ . . . this exit poll is right, then David Cameron has won a very handsome victory,” Gove said on the BBC. And on the streets, Tories were echoing that view.

“I’m celebrating,” said ­Lawrence Worsley, a 48-year-old project manager, as he held a pint of beer high in the air at the Blue Boar, a swanky restaurant close to the Conservative and Labor party headquarters in London.

“I think people who were undecided came to the polls and made their mind up at the last minute that it’s best to stick with what you know, something that has worked,” he said.

When the exit poll was announced on the BBC, a cluster of suited patrons watching on the restaurant’s big-screen televisions cheered, while others gasped audibly.

By early Friday, there was speculation that the Conservatives might be able to win an outright majority in the new Parliament, though that might not be known until much later in the day, if then.

If they fall short, they will face a choice of whether to go into a formal coalition with other parties or to try to forge ahead with a minority government that wins support from allies on key votes. Whatever the final results, the Conservatives will find themselves trying to govern a country that is more regionally divided than it has been in many years.

Pre-election polls had predicted problems for the Liberal Democrats, but the collapse was even greater than anticipated. The exit poll projected that the party would end up with just 10 seats, down from 57 in 2010. Party leader Nick Clegg was one of the few to retain his seat, but he called it “a cruel and punishing night” for his party and hinted that he might step down.

Early in the evening, Ed Balls, Labor’s top economic official, said his party held out hope of forming a workable government. But analysts suggested that such a clear margin in the Conservatives’ favor would make it nearly impossible for Labor to claim a mandate, and such talk faded as the hours wore on.

The SNP was forecast to win 58 seats out of 59 in Scotland — a staggering result, if it holds. That would make it the third-largest party in the new Parliament behind the Conservatives and Labor.

The anti-immigration U.K. ­Independence Party (UKIP) was running third in the overall national vote, but it was struggling under Britain’s first-past-the-post voting system to turn support into seats. Exit polls predicted the party would win just two, and party leader Nigel Farage, seeking a seat, was in an extremely tough race.

The Green Party was also predicted to win two seats. The growing role of smaller parties reflected an increasingly fragmented electorate.

“We’re into uncharted territory,” said Andrew Russell, chairman of the politics department at the University of Manchester. “We have an electoral system that is designed to produce a certain winner and to sustain two parties. But now it’s throwing up a whole multiplicity of parties.”

Thursday’s results followed a campaign that laid bare fundamental questions about Britain’s identity that could become even more divisive in the years ahead. At a time of growing U.S. frustration with its closest ally, Britain may be drawn even further inward and away from global affairs.

The Scottish nationalists, suddenly a major player in London after Thursday’s vote, want to break up the United Kingdom — and have often used a Tory government that is unpopular among Scots as their strongest argument for independence.

UKIP has campaigned to take Britain out of the E.U. and is likely to use its toehold in the House of Commons to force the issue.

[A new political order in Scotland threatens to upend the British election ]

Cameron has promised a referendum on E.U. membership by 2017 and has said he will not compromise on that vow.

[11 weird memes that help explain the British election ]

The rules require that the governing party command a majority of support in the House of Commons. In theory, that would mean 326 seats. In practice, though, because some members don’t vote, a majority is 323 seats.

[The British election is the most unpredictable in a generation. Here’s why. ]

Before the campaign began, most analysts had expected that Cameron would coast to a relatively easy reelection, boosted by a recovering economy and a significantly higher favorability rating than Miliband.

Miliband performed better than many expected in the harsh glare of the campaign, emphasizing the growing divide between rich and poor at a time of minimal wage growth and deep cuts to government assistance programs.

But in the final days of the campaign, with the polls still tied, Cameron became more passionate on the campaign trail — and more negative, predicting that Labor would lead the country to economic calamity if voted into office.

That message appeared to have resonated, at least with some. After voting Tory in the tony North London neighborhood of Hampstead on Thursday, Norma Bainbridge said her decision came down to a single word: “money.”

“The Conservatives are quite clever with it,” said the 80-year-old. “Labor got rid of it. We were broke.”

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