Voters went to the polls on Thursday in an election that will pave the way for Brexit under Prime Minister Boris Johnson or propel Britain towards another referendum that could ultimately reverse the decision to leave the EU.

After failing to deliver Brexit by an October 31 deadline, Johnson called the election to break what he cast as political paralysis that had thwarted Britain’s departure and sapped confidence in the economy.

The face of the “Leave” campaign in the 2016 referendum, 55-year-old Johnson fought the election under the slogan of “Get Brexit Done”, promising to end the deadlock and spend more on health, education and the police.

His main opponent, Labour leader Jeremy Corbyn, 70, promised higher public spending, nationalisation of key services, taxes on the wealthy and another referendum on Brexit.

All major opinion polls suggest Johnson will win, though pollsters got the 2016 referendum wrong and their models predict outcomes ranging from a hung parliament to the biggest Conservative landslide since the era of Margaret Thatcher.

Seven eve-of-election opinion polls published on Wednesday showed the Conservatives ahead of Labour by an average of nearly 10 points although Labour narrowed the gap in four of them.

“We could have a Conservative majority government which will get Brexit done and unleash Britain’s potential,” Johnson told campaigners. “This election is our chance to end the gridlock but the result is on a knife-edge.”

Corbyn said the Conservatives were the party of “billionaires” while Labour represented the many.

“You can vote for despair and vote for the dishonesty of this government, or you can vote Labour and get a government that can bring hope to the future,” he said.

Polls opened at 0700 GMT and will close at 2200 GMT when an exit poll will give the first indications of the result.

Official results from the bulk of the UK’s 650 constituencies begin to come in from 2300 GMT to 0500 GMT.

While Brexit framed the UK’s first December election since 1923, the tortuous exit from the EU has variously fatigued, enthused and enraged voters while eroding loyalties to the two major parties.

A majority would allow Johnson to lead the country out of the club it joined in 1973, but Brexit would be far from over. He must negotiate a trade agreement with the EU in a self-imposed deadline of 11 months.

After January 31, Britain would enter a transition period during which it would negotiate a new relationship with the 27 EU members. He has pledged to do that by the end of 2020.

Sterling markets are pricing in a Johnson win and the pound was up against the dollar and the euro in early trading on Thursday.

But two historic referendums — on Scottish independence in 2014 and Brexit in 2016 - and two national elections in 2015 and 2017 have delivered often unexpected results that ushered in political crises.

The election pitches two of the most unconventional British politicians of recent years against each other. Both have been repeatedly written off by opponents and both offer starkly different visions for the world's fifth-largest economy.

Johnson’s pitch is Brexit but he shrank from anything more radical in a heavily choreographed campaign. Corbyn pitched what he calls a radical transformation for a country long wedded to free-market liberalism.

Johnson, the New York-born former mayor of London, won the top job in July. His predecessor, Theresa May, resigned after failing to get parliamentary backing for her Brexit deal with the EU and then losing her party’s majority in a snap election.