LONDON — U.K. election nights are known for throwing up surprises.

Thanks to Britain's first-past-the-post electoral system, every poll sees Cabinet ministers and rising stars ousted by disgruntled constituents or swept up by an unstoppable shift in the national mood.

December's election is widely expected to be less predictable than any since World War II. “All the academic evidence shows that there’s more voters moving between parties than ever before,” according to Chris Curtis, political research manager at YouGov. “At different points this year, we’ve had four different political parties in first place.”

“The polls at the moment show the Conservatives with a healthy lead over Labour,” said Joe Twyman, co-founder of the public opinion consultancy DeltaPoll. “In normal circumstances you would look at that and think that’s pretty good, but these are not normal circumstances. The key here is the fact that the election could be divided around different lines.”

Here are 12 big names who, depending on which way the electorate swings, could find themselves out in the cold.

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Boris Johnson

Very unusually for a U.K. prime minister, Boris Johnson represents a marginal constituency.

His majority in Uxbridge and South Ruislip, an area of northwest London, was slashed by half to just over 5,000 in 2017. It’s a Brexit-supporting area, but one that has a large student population and has been undergoing demographic change.

The prime minister's spokesman is adamant that Johnson will not look to move to a safer seat.

Will Tanner, director of the think tank Onward, said: “We are seeing demographic changes playing an increasing role in a number of seats,” particularly in London constituencies that are becoming “quite rapidly younger.”

“Their profiles are moving away from the Conservative Party as people’s age strongly dictates voting preference,” Tanner said.

“Rather than income and class, age and education are the two factors which most strongly determine vote intention, with younger, degree-educated people voting for the Labour Party typically, and older, less-educated people voting for the Conservatives.”

In the unlikely event that Johnson is ousted in Uxbridge, he could only continue as prime minister by winning a by-election in another seat or by being appointed to the House of Lords.

Iain Duncan Smith

It’s much the same story in the former Tory leader Iain Duncan Smith’s London constituency of Chingford and Woodford Green.

The area voted very narrowly to remain in the EU, but Duncan Smith is an arch-Brexiteer. Now he is fighting to retain a majority of just 2,400, which has been slashed from nearly 13,000 in 2010.

According to Twyman, the Conservatives are hoping that in Tory-held, Remain-supporting seats such as this one “the fear of a Jeremy Corbyn government will be enough to ensure that party loyalty trumps Brexit loyalty.”

Theresa Villiers

Environment Secretary Theresa Villiers is fighting to hold on with a tiny majority of 353 in Chipping Barnet, north London.

The Cabinet minister is a hard Brexiteer who voted against Theresa May’s deal three times, and is said to have had serious reservations about Boris Johnson’s deal too. But the constituency she represents voted by nearly 60 percent to Remain.

Twyman said that “in younger, affluent, socially liberal seats you do tend to see higher levels of Remain support and higher levels of Remain support makes things more difficult [for Tory candidates].”

Dominic Grieve

On the other side of the coin is Remainer and former Attorney General Dominic Grieve.

Grieve, who has been instrumental in the numerous parliamentary rebellions to prevent the U.K. leaving the European Union without a deal, will contest his Beaconsfield constituency as an independent. He lost the Tory whip in September.

Grieve has been the Beaconsfield MP since 1997, and voters’ familiarity with him could be an advantage. However, his Conservative majority was nearly 25,000 and it will be exceedingly difficult for him to make real inroads as an independent in such a solidly blue area in leafy Buckinghamshire, 25 miles to the northwest of the capital.

He is, however, the first beneficiary of the so-called Remain alliance pact, with the Liberal Democrats announcing they will stand aside in the constituency to avoid dividing support between two candidates who both support a second referendum.

“You could have a situation where you’ve got the official Conservative candidate, Dominic Grieve, as an unofficial Remain Conservative candidate, and the Brexit Party candidate, all splitting the vote,” Twyman said.

Anna Soubry

Another ex-Tory arch-Remainer, Anna Soubry left the Conservative Party of her own accord earlier this year. She went on to lead the Independent Group for Change, made up of a handful of pro-EU exiles from the major parties.

Soubry will contest her Broxtowe constituency, a Labour-Conservative marginal that voted narrowly to leave the EU. But as an independent, she will struggle to retain the seat.

Jo Swinson

Jo Swinson says she can be the U.K.’s next prime minister — but she will have to keep hold of her constituency first.

The Liberal Democrat leader has a majority of just over 5,000 in her Scottish constituency of East Dunbartonshire, which she won back from the Scottish National Party in 2017.

The SNP had temporarily unseated Swinson in 2015 and the party is once again riding high in the polls.

However, Curtis said that polling suggests Swinson will keep her seat. “What we tend to see in Scotland is a big swing to the SNP against all parties except the Liberal Democrats,” he said. “There isn’t really a Lib Dems to SNP swing, so you’d expect if that plays out in a uniform basis, that the Lib Dems hold all their seats in Scotland whilst everyone else gets almost completely wiped out.”

Dennis Skinner

Ex-miner and Labour MP Dennis Skinner is set to become the Father of the House — the longest continuously serving MP in the Commons — if he is reelected this year.

But his Bolsover seat is one of several northern Brexit-voting constituencies that the Conservatives hope to win off Labour. Skinner’s majority was slashed by half in 2017, dropping to just over 5,000, despite the fact that he is a Brexiteer.

Tanner said that seats in the north of England with older populations “are actually moving towards the Conservative Party.”

“Some of the other demographics are coming into play quite strongly too — the fact that lots of places in the north of England have relatively low levels of people going to university, which is a strong indicator of Conservative voting preference, and also a stronger contingent of voters who are white rather than ethnic minorities,” Tanner added.

Yvette Cooper

Another Labour MP in a northern Brexit-backing seat, Yvette Cooper has been instrumental in the parliamentary effort to stop no-deal Brexit.

But she represents the heavily Brexit-voting Normanton, Pontefract and Castleford, a constituency which has been specifically targeted by the Brexit Party. Her majority is just under 15,000.

Her husband, the former Shadow Chancellor Ed Balls, unexpectedly lost his own seat in a neighboring constituency in the 2015 general election.

Frank Field

Veteran Birkenhead MP Frank Field resigned the Labour whip in 2018 because of political differences with leader Jeremy Corbyn and will stand again for his seat as an independent.

As MPs go, he will have one of the strongest levels of personal support, given he has represented the area since 1979.

But a personal vote is rarely enough. “Very well known MPs tend to benefit but they are few and far between,” Twyman said.

Emily Thornberry

It’s not just Labour’s Brexit-backing seats that are vulnerable. Heavily Remain-voting areas, including those in London, are being targeted by the Lib Dems, who are campaigning to revoke Brexit altogether.

Shadow Foreign Secretary Emily Thornberry may have a majority of more than 20,000 in Islington South and Finsbury, but if there is a huge swing toward the Lib Dems she may find herself in trouble there.

She was nearly unseated by the Lib Dem candidate in 2005, with her majority cut to less than 500.

“On current polling, the Labour vote share could basically halve and the Liberal Democrat vote share could basically double,” Curtis said. “If we see a further surge from the Lib Dems during this campaign, that suddenly does start to threaten the Islington seats, for example Emily Thornberry’s.”

“There’s some really particular demographics where the Lib Dems are doing well, graduates being the most obvious example, where they’re now neck and neck with the Labour Party for first place,” according to Curtis.

“In places that contain a lot of those type of voters, we can see some really big swings from Labour to the Lib Dems. It could mean Lib Dems going from third place to taking constituencies in inner London.”

Nigel Dodds

Northern Ireland's Democratic Unionist Party's leader in Westminster, Nigel Dodds represents the marginal seat of Belfast North, with a majority of just 2,000 to defend.

The constituency is socially liberal and supported Remain in the 2016 referendum, with a large youthful population, including lots of university students. It’s also split fairly evenly between Protestants and Catholics.

It’s a key target for Sinn Fein in this election. Their chances are boosted by the fast that the Ulster Unionist Party is insisting on fielding a candidate in the constituency, despite arguments that this will split the unionist vote.

Ian Blackford

Although the Scottish National Party is on strong footing in Scotland, its Westminster leader Ian Blackford could find himself the victim of an opposition party stitch-up.

He has a majority of just under 6,000 to defend in Ross, Skye and Lochaber. The Times reported this week that Labour and the Tories are forming an informal pact to unseat Blackford by sitting back and letting the Lib Dems work hard to take the seat.

The constituency is considered Lib Dem heartland, and was represented by the party’s former leader Charles Kennedy for a decade.

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