The U.K. is set to hold an emergency general election in six weeks’ time after Prime Minister Boris Johnson won backing in Parliament to trigger a poll to end the Brexit crisis paralyzing the country.

The vote will be held on Dec. 12 and it will be the third time the country has gone to the polls in four and-a-half-years.

At a time of unprecedented political and constitutional upheaval, the outcome of the contest is set to be harder than ever to predict. Yet with the U.K. still locked in limbo, unable to complete its tortured three-year divorce from the European Union, the election is likely to become a proxy referendum on Brexit.

“There is only one way to get Brexit done in the face of this unrelenting parliamentary obstructionism,” Johnson told the House of Commons earlier on Tuesday. “That is, Mr Speaker, to refresh this Parliament and give the people a choice.”

The campaign will pit Johnson, the charismatic and controversial face of the pro-Brexit movement, against the radical left-wing Labour leader Jeremy Corbyn, who defied pundits and pollsters and nearly won power two years ago.

On Tuesday, Johnson won a vote in the House of Commons for a law enabling a Dec. 12 election to take place. That law must be approved in the House of Lords before it comes into force, but it is now unlikely to be blocked.