In one of the most unpredictable elections in decades, Boris Johnson’s route to a Commons majority goes through places like Darlington. The Tees Valley market town has been solidly Labour since 1992, but its 56.2% vote to leave the EU put most voters at odds with its MP Jenny Chapman, the shadow Brexit minister. Two years ago Chapman slightly increased her majority, to 3,280 votes, but so much has changed since 2017. And while the changes on the national stage are the most obvious, the constituency’s effect on the balance of power may ultimately be down to a much more local set of concerns.

Facebook Twitter Pinterest Darlington’s effect on the balance of power may be down to local concerns. Photograph: Richard Saker/The Observer

Earlier this year Darlington upended 40 years of political tradition and voted the Conservative party into the council, becoming the first Tory-run local authority in Labour’s stronghold of shipbuilding and steelworks. The political tremors ran along the River Tees, removing Labour from office in Middlesbrough, Hartlepool, Stockton and Redcar and Cleveland. When Ben Houchen, the region’s Conservative mayor, won his surprise election in 2017, all five council leaders in his area were Labour. Today there are none.

While Brexit has undoubtedly broken down traditional party allegiances, there are other factors in play. In Darlington, the demographics of the town are changing and Labour can no longer rely on its once-loyal support. A series of controversial decisions by the Labour council turned their own voters against them in May, and there is a distinct possibility that Darlington will elect a Conservative MP on 12 December, the first since Margaret Thatcher’s premiership. If that happens, Labour could be locked out of power here for a generation.

To understand the current political landscape in Darlington you have to go back to 2016. As the EU referendum battle raged across the country, the headlines here were dominated by one issue: the council’s determined attempt to close the town’s cherished library in the name of austerity.

Based in a handsome Grade II-listed building, the library had been a permanent fixture of the town since 1885. The building was gifted by the town’s founding father, the Quaker industrialist Edward Pease, and is bound by a decades-old covenant to be used as a library forever. Generations of Darlingtonians learned to read and write in the building, the only full-time library for a town of more than 105,000 people and the second busiest in north-east England.

Facebook Twitter Pinterest The 56.2% vote to leave in Darlington put most voters at odds with its MP Jenny Chapman, the shadow Brexit minister. Photograph: Alamy Stock Photo

Sheila Harris, 67, has supported Labour all her life. But she was disgusted by her own party’s actions – even if the cuts that ultimately prompted them were a choice of the Conservative government. And, she says, the announcement caused uproar. “It’s hard to understand the feeling in the town,” she said. “We don’t have a town museum. It’s part of the history of the town. It felt like the final straw.”

A campaign group was formed. Protesters gathered in their hundreds, dozens packed out public meetings, and more than 6,000 people signed a petition in the Northern Echo. Councillors voted through the multi-million pound raft of cuts all the same. The campaigners took the council to court, eventually saving the library after a two-and-a-half year battle.

Some observers might view the fight over the library as a proxy for the underlying factors that have been linked to Brexit: years of cuts, a sense that people have lost control over their own lives, and a pervading belief that places far from London have been forgotten. But in Darlington, it did not feel like part of a sweeping national story. Instead, a campaign ostensibly about a library became a focus for other long-held concerns about the direction of the town.

The library had been saved, yes. But the hospital’s accident and emergency department had been threatened with closure. High street names including British Home Stores, TK Maxx, and Marks & Spencer had all been lost. Many felt the town was being stripped of its heritage after the closure in 2012 of its Arts Centre, a huge Victorian building that was home to about 100 community groups and that hosted 250 plays a year.

Beryl Hankin, 75, has run a boutique selling everything from postcards to dreamcatchers in Darlington for 47 years. “A town isn’t all about commercial success – although that’s very nice – it’s about a sense of place,” she said. “Everything seems to have declined. The recession and then austerity - it just all clicks together to make it harder… I cry every time I walk down that high row [of shops in the town centre]. And I know that’s stupid, but I know what it could’ve been - now it’s just like everywhere else.”

There was anger, too, about an ill-conceived £12m road improvement scheme and the former council chief executive’s £188,000 salary, more than the prime minister and seven times the average Darlington wage.

It was felt that politicians were just not listening to people. For Harris, whose great-grandfather founded the Labour party in nearby Hartlepool, the feeling cut deep. “I felt let down. Not by the [library] decision, but the fact that people who you vote for were not listening to the people they were supposed to represent. When I wrote to them, they didn’t even reply. It was the loss of trust,” she said.

Facebook Twitter Pinterest Rough sleepers at a bus shelter in Darlington, where only a few residents say their top priority is Brexit. Photograph: Richard Saker/The Observer

Harris, a former charity manager, led the campaign with Yvonne Richardson, a 71-year-old who is known for her volunteer work in her local community. The pair are from opposite ends of the political spectrum, and voted different ways in the EU referendum. But they were united by a feeling of being ignored and spoken down to by their local political leaders. “It’s a symptom of the ‘We know better’ attitude to people,” Richardson said.

Darlington is a town of contrasts. Beyond its cobblestone centre, with its handsome market square and miniature Big Ben, there are leafy roads of Edwardian townhouses next to rows of tired-looking terraces. A six-bedroom semi in the West End would cost £300,000, while a two-up-two-down on an adjacent street would sell for £50,000. It has a two-Michelin star restaurant, and a food bank where about 50 people queue on a Friday night to survive the weekend. Life expectancy is 12 years lower for men in the most deprived areas of the town compared with those in the wealthiest.

Economically, Darlington punches above its weight. Its economy has grown faster than its north-east neighbours, with a new £38m national biologics manufacturing centre the jewel in its crown. A sprawling Amazon distribution site is expected to open next year, promising as many as 3,500 jobs.

Facebook Twitter Pinterest Beryl Hankin in her shop Guru Boutique in Darlington, which has been a Labour stronghold since 1992. Photograph: Richard Saker/The Observer

Away from the eye-catching numbers, though, there is a sense that life for many has got worse, not better. Unemployment is double the national average in Darlington and house prices have stagnated, creeping up 9% compared with 29% in the rest of the UK. The council, which recorded a £16m deficit last year, has been forced to make £57m worth of savings and lose 747 jobs due to cuts in government funding since 2010.

The council’s U-turn on the library late last year wasn’t enough to save it at the polls in May. The campaign appears to have given rise to other grassroots groups, organising on Facebook against the new Conservative council’s plans to build at least 10,000 new homes in the town. Last week the council said it was temporarily shelving the proposals following concerns that its road network would struggle to cope. The timing of the announcement – on the eve of the election – reprised old feelings of a loss of trust in politics.

“I’ve met councillors in our area and they’ve promised they would tear up this local plan. We helped them get in and now they ignore us – it’s quite worrying,” said David Clark, a 53-year-old financial adviser who is campaigning against plans to build a 4,500-home “garden village” on his doorstep.

Clark said he was a loyal Tory voter and wanted to leave the EU, but he can no longer bring himself to vote for the Conservatives due to a “loss of trust” locally. “I’m all for Brexit and the Lib Dems and Greens are for remain but you’ve got to think what’s [happening] on your doorstep,” he said. “It’s starting to make me think for the future generations.”

Facebook Twitter Pinterest Local man Paul Howell outside Darlington’s library, in the town where Labour has a fight on its hands. Photograph: Richard Saker/The Observer

The Conservatives might not convince Clark but their candidate, Peter Gibson, feels the party has the best chance of winning the seat in a generation. The local party has doubled its membership in the past year, to around 500 people, and delivered 100,000 leaflets in the last month – many focusing on local issues rather than Brexit. On Facebook, the Tories have outspent Labour by four to one since October 2018, an analysis shows, with messages on Brexit and local issues targeted mainly at middle-aged men. Labour’s Facebook advertising for Jenny Chapman, on the other hand, has been shown more to middle-aged women.

More than 50 Darlington residents who contacted the Guardian for this article cited a range of issues as their biggest concerns, including the NHS, lower standards of living and public sector pay freezes. Only a few said their top priority was Brexit.

Just as David Clark is thinking of giving up on the Conservatives, Sheila Harris has lost her faith in Labour. Sheltering from an afternoon downpour in the library, she said she wanted to support a remain party, but felt unable to return to her longtime political home: instead, she was considering voting for the Lib Dems.

Yvonne Richardson, on the other hand, who has always been a floating voter, said she would vote for the Conservatives this time – partly because of their Brexit stance, but also because they helped her clean out the local park. In all three cases, political decisions that have been broadly attributed to the fight over Brexit seemed just as crucially linked to questions that were much closer to home.

“None of them deserve the trust except for Boris,” said Richardson. Harris disagreed: “Don’t put that down as a joint quotation because I don’t agree. We came together to save the library but we all have different opinions. To be honest, that made us stronger.”