LONDON — Boris Johnson is on course to win 368 seats in Britain's election, according to an exit poll by U.K. broadcasters, potentially giving his Conservative Party a majority of 86, above what many pundits predicted.

It means Johnson would likely be able to deliver on his promise to take Britain out of the European Union.

Johnson all but declared victory, urging supporters to enjoy the night.

"I hope you enjoy a celebration tonight," he said in an email to party members. "You powered this campaign. We couldn't have done it without you."

Thank you to everyone across our great country who voted, who volunteered, who stood as candidates. We live in the greatest democracy in the world. pic.twitter.com/1MuEMXqWHq — Boris Johnson (@BorisJohnson) December 12, 2019

Conservative Party insiders said the forecast was way ahead of expectations.

“That’s a lot better than anyone expected," said one insider. "People here are happy but are being cautious because exit polls have been wrong before.

"Champagne corks are not going to be popping anytime soon, but, if the result is anywhere close to this, then it will be a very good night and we can get on with Brexit.”

The BBC/Sky/ITV poll predicted that Johnson's party would win 42 more seats than the 326 needed for an absolute majority in the House of Commons, putting him on course for the largest margin for a Conservative leader since Margaret Thatcher in the 1980s.

As well as Johnson, the other big winners look likely to be Scottish Nationalists who are on course to pick up an extra 20 seats. That means the S.N.P. could win 55 of the 59 seats north of the border, strengthening their demand for another referendum on independence.

Labour is predicted to lose 52 seats overall, leaving it with 191 MPs, while the Scottish National Party will finish with 55, the Liberal Democrats with 13, and Nigel Farage's Brexit Party with none.

The result suggests Johnson's message of public spending coupled with a Brexit push resonated with blue-collar voters who backed leaving the European Union but have seen politicians in London locked in three years of wrangling.

The election pitted Johnson's promise to get Brexit done against Jeremy Corbyn's Labour Party, which had shifted to the left.

The prediction means a long night for the Labour Party and its supporters.

Labour peer Stewart Wood, a former adviser to Ed Miliband, tweeted: "For 30 years, the conventional wisdom was that the Tory Party would be mortally split by the national question of EU membership. Turned out that it is the Labour Party that suffered the most."