SEDGEFIELD, England — Dehenna Davison is a 23-year-old Tory who works in a computer game shop in Hull. On June 8 she hopes to win Tony Blair’s old seat in parliament in a victory which would redefine British politics after Brexit.

It is an ambition that would have seemed barely credible until last year’s referendum — a poll that tore through British politics, ripping up the old political landscape and leaving vast tracts of formerly safe Labour territory vulnerable to a Tory takeover.

A victory for the Tories here — a seat held by Labour for 86 years, 24 of those by the former British prime minister — would represent a historic realignment in U.K. politics. It would be evidence of something far more fundamental than a low ebb for the British left.

Even during the height of Margaret Thatcher’s dominance in the 1980s, the English north-east was consistently high ground for Labour. In 1983, the year of Thatcher’s first landslide victory, Blair won 47.6 percent of the vote in Sedgefield. The party held a similar share of the vote two years ago when Blair’s successor Phil Wilson was returned with 47.2 percent of the votes cast.

This time, however, no one studying the polling or involved in either the Tory or Labour campaigns nationally thinks Sedgefield or its surrounding constituencies are beyond Prime Minister Theresa May’s reach. Last summer’s Brexit referendum triggered a surge in support for the Tories alongside UKIP’s collapse, putting at least 80 marginal Labour seats in play across England and Wales.

The voters in these seats used to be Labour. No longer. “Most of these voters were tribal,” said Andrew Cooper, a pollster who worked for David Cameron when he was prime minister, and founded the consumer research agency Populus. “They always voted Labour because Labour was seen as fundamentally on the side of people like them. They no longer believe that. And for most of them what broke that tribal loyalty was Brexit.”

It is these battleground constituencies — often poor, relatively rural, mostly white — that will determine the extent of May’s expected victory next month. May is hoping to extend her reach into the white working class that has largely stuck with Labour but has in recent years drifted over to UKIP as they came to feel alienated by the party’s perceived liberal values, particularly on Europe and immigration.

“If Labour crashes in a big way, Sedgefield is interesting,” said Matthew Goodwin, a polling expert and academic. “I would suggest the entire concept of the Labour heartland will look a little bit different after the next election. The million-dollar question is how low will Labour go."

When Labour last crashed in this way in the wake of 2014’s independence referendum in Scotland, Mhairi Black, a 20-year-old student from Glasgow was swept into parliament by a Scottish National Party surge that left Labour with just one MP north of the border.

Like Black, Davison has an unlikely biography for someone heading for Westminster. Her father was killed with a single punch in a pub when she just 13. Her mother was a nursery nurse in Sheffield but is now out of work. She follows Taylor Swift and Katy Perry on Twitter. The year she was born, 1994, Blair was elected Labour leader, Jeremy Corbyn was a fringe left-winger on the backbenches, and May was licking her wounds after losing a second bid to become an MP in Barking.

Even more unlikely, however, is that Davison’s in with a chance.

Standing with May

On a visit to the battleground towns of Sedgefield, Darlington and Bishop Auckland, signs of Labour’s decline are not hard to find. On outings with candidates, POLITICO discovered broad contentment with May and broad, but mostly apathetic satisfaction about her implementation of Brexit. When it came to Jeremy Corbyn it was mostly an instinctive, almost guttural incomprehension rather than outright hostility. “It’s a cultural thing,” said one Labour MP from the north-east who did not want to be named. “It’s nothing to do with his policies. They just think he’s too London.”

The depths of the division in the Labour Party were exposed at last year’s Durham Miners’ Gala, an annual gathering of trades unionists that has become a mecca for left-wing activists. Wilson, Labour’s Sedgefield candidate who was raised in Durham, the son of a miner, was barred from the platform and told he was not welcome because he voted for Corbyn to be replaced as party leader. Corbyn, a middle-class boy from the shires in southern England was welcomed on stage.

Across the region, the Conservative strategy is clear: Theresa May.

In neighboring Bishop Auckland, Tory candidate Christopher Adams declares on his website that he is “Standing with Theresa May for Bishop Auckland.” In Sedgefield, Davison’s slogan is “Standing with Theresa May in Sedgefield.”

Down the road in Darlington, Tory candidate Peter Cuthbertson was canvassing in a formerly rock-solid Labour ward. “Hello, I’m Peter Cuthbertson,” he said to every voter he met as he went door-to-door in an estate of tidy, three-bedroom, semi-detached family homes. “I’m here representing Theresa May. I’m standing to be your MP.”

Cuthbertson said he has been amazed by the positive welcome he has received compared to 2015 when he ran and lost. He was finding little support for Labour and widespread, if apathetic, sympathy for the Tories. (Full disclosure: the author attended college and university with Cuthbertson. His parents are Labour Party members in Sedgefield. Wilson, Labour’s candidate there, is a family friend.)

“The fundamental coalition that held Labour together has broken down” — Jacob Rees-Mogg, Conservative MP and influential Brexiteer

None of the candidates who spoke to POLITICO said Brexit was the main issue being raised by voters on the doorstep but all said the contrast between May and Corbyn was mentioned repeatedly.

“They’re just running on Theresa May,” said Helen Goodman, the Labour candidate in Bishop Auckland and its MP until May dissolved parliament after calling the new election. With Brexit underway, the issue is no longer driving the discussion, providing what she saw as an opening for Labour to talk about economic issues. “I think the Tories are going to find it tougher than they imagine,” she said.

“Hello, do you know about the cuts the Tories are making to the school budget?” Goodman asked parents collecting their children from school. Most took a flyer — which showed a drop in the school’s budget of £800 per pupil — but many seemed entirely uninterested.

Only one person, a father wearing a “Brawlers Gym Muay Thai MMA” T-shirt seemed faintly hostile. “I’m UKIP, me,” he said to a friend just inside the school gates.

According to Douglas Carswell, the former Conservative then UKIP MP who lost to Blair in Sedgefield in 2001, May is crucial for the Tories but said that if it had not been for the Brexit referendum, tribal loyalties in seats like Sedgefield would have been impossible to break.

“The experience of standing in Sedgefield had quite a profound impact on me,” he said. “I was constantly baffled that people who don’t have a liberal-left view on pretty much anything but who would then vote for someone who, to me, epitomized the liberal left view of the elites in London.”

It was the referendum, he added, that brought this conflict into the open. “Everyone talks about the schism being inevitable, but this schism has always been there,” he said.

Jacob Rees-Mogg, the Conservative MP and influential Brexiteer who mentored Davison when she spent a year working in his parliamentary office as part of her university degree, shares Carswell’s view. “The fundamental coalition that held Labour together has broken down,” he said. “The Fabian socialists of a Metropolitan view and the bulk of its voters no longer really like each other.”

Cooper, the pollster, has produced private demographic analysis seen by POLITICO which puts Sedgefield squarely in the ranks of former safe Labour seats in northern and central England which are now at risk.

The data reveals the growing significance of identity politics, showing Tory strength in rural English constituencies which are both affluent and white. In contrast, Labour performs best in the poorest inner cities.

The battleground constituencies which will decide next month’s election are those in the middle – often poor, relatively rural, small towns with a predominantly white population. May is hoping to push deeper into these working class communities which have felt alienated by Labour’s perceived liberal values, Cooper said.

“With that enormously difficult start to life, she is so impressive and capable” — Rees-Mogg on Dehenna Davison

In Sedgefield, like much of England’s former industrial heartlands, much of this alienated vote went to UKIP and made up the difference between Labour’s support and the Conservatives’.

Taken together, the Tory and UKIP vote in Sedgefield is 17,858 – 417 short of Labour’s 18,275. To capture the seat, the Tories would need at least half UKIP’s 6,426 votes, a sizeable number of Labour supporters to stay at home, and for 1,000-2,000 Labour voters to turn blue – 5-10 percent of Wilson’s voters in 2015. Tough but not impossible. Indeed, the Tories seem to believe they have a chance. Philip Hammond, the chancellor of the exchequer, was in the constituency this week campaigning with Davison.

Matthew Goodwin said the biggest unknown in areas such as Sedgefield is what UKIP’s supporters will do now that Brexit in underway.

“What we don’t know in seats like Sedgefield is will UKIP voters stay more loyal because they don’t like the Tories?” he said. “Whereas in the south will UKIP voters just completely defect en masse allowing the Conservatives to build staggering majorities in Kent and Lincolnshire. [In the north] we don’t yet know.”

Hanging on

There are reasons to think that Labour might hang on in Sedgefield. While the party is far behind the Tories in the polls, its support is not much lower than it was during the last election. The party hovers at about 27 percent nationally, compared to the 30 percent of the votes it received in 2015. In last week’s local election, the party (barely) managed to cling to control of the county council here.

Labour candidate Wilson, an outspoken critic of Corbyn, who worked for Blair before succeeding him in 2007, will be hard to characterize as a lefty London liberal. He was born and raised in the constituency and sent his children to the local state school. His weak spot is his active support for Remain in the Brexit referendum. Sedgefield voted 60-40 to leave.

"This is obviously going to be a tough fight," said Wilson, before launching into a list of his advantages. “I’m from Sedgefield. I’ve lived here all my life and love the area and its people. I’ve never wanted to represent anywhere else. It’s either me or a 23-year-old Conservative student from Hull.”

Indeed, in nominating a 23-year-old shop assistant, the Tories might have given a hint of their expectations.

Conservative officials in the north-east said the constituency was less of a target than others in the region — like Bishop Auckland, Darlington and Middlesbrough South — where Labour was weaker in 2015. Those, they said, will be “bombarded” by the party over the coming four weeks.

Conservative MP Rees-Mogg, for whom Davison worked in parliament, insists she is “formidably able” and has a bright future, whether or not she wins next month.

Dehenna Davison understands the significance her victory would represent and doesn’t hide her awe at the possibility of a scalp at the heart of Blair country.

“With that enormously difficult start to life, she is so impressive and capable,” said Ress-Mogg. “Perhaps that’s why she was so empathetic with the constituents she dealt with on my behalf. She is a very remarkable person.”

Davison got involved in Tory politics at 16 while at school — a private girls’ school in Sheffield which she attended on a full scholarship. “It was about the values: hard work and aspiration,” she said, referring to what she sees as Conservative Party principles. “I thought, hang on that’s me and that’s my family. I rang up my local association and said can I come along and help you?”

In 2015, she stood in Hull North. She finished third behind Labour, with UKIP in second, but she increased the share of the Tory vote. This time around, the Conservative Central Office handed the Sedgefield Conservative association a shortlist of three candidates. Davison was chosen in hustings on April 27.

Davison understands the significance her victory would represent and doesn’t hide her awe at the possibility of a scalp at the heart of Blair country. The first thing she did after getting to Sedgefield was to visit the Trimdon Working Men’s Club, a former miner’s pub where Blair once held court, hosting the French prime minister in 1998 and announcing his retirement in 2007. “It’s iconic,” said Davison.

Four weeks out from the election, Davison insists she can win.

“It’s actually happening,” she said. “People saying, I’ve voted Labour all my life and this time I just can’t. We ask them why. It’s the Corbyn effect and the Theresa May effect.”