As Nigel Farage cut the ribbon on Reform UK’s byelection headquarters in Greater Manchester this week, Labour’s candidate, Angeliki Stogia, sat tearfully in a cafe nearby.

Politicians do not often show their emotion but for Stogia, who arrived in Britain as a student from Greece in 1995, this is personal. “I am angry,” she said of Farage’s party. “I am very, very angry. How dare they come here and spread this division?”

Her voice breaking, she added: “For them, this is a show. For me, this is my community. This is my people.”

Westminster byelections are often bruising affairs but the battle for Gorton and Denton is one of the most unpredictable contests, with the highest stakes, in years. Labour is fighting both Reform UK and the Green party to cling on to its 13,000-vote majority after the retirement last month of Andrew Gwynne, who stepped down after the “vile” Trigger Me Timbers WhatsApp scandal.

Starmer’s government is engulfed in crisis over Peter Mandelson’s links to Jeffrey Epstein, and defeat on 26 February is likely to prompt further calls for the prime minister to quit.

Labour has dominated this diverse patch of south-east Manchester for decades. But less than three weeks before polling day, the Green party is the bookies’ favourite.

Sheltering from a biting wind in Denton this week, Stogia accused the Greens of “lying” to the public by printing a “misleading” chart on its leaflets suggesting that only they could beat Reform UK.

She was worried, she said, that in such a tight contest it could only benefit Reform. In last year’s Runcorn and Helsby byelection, a split vote on the left allowed Farage’s party to win by six votes.

“I am very disappointed with what they’re putting out, because in Runcorn we lost by six votes,” said the Labour councillor. “It is the progressive side that has lost by six votes.

“I worry that we will lose it. Every Green vote is going to make Reform very happy.”

Prof Robert Ford, of the University of Manchester, said the key to understanding this byelection was that for every vote on the Farage-friendly Denton side, there were two votes on the larger, more diverse and left-leaning Manchester side.

In 2024, nearly 80% of the constituency backed a party on the left. The only realistic way that Reform UK can win, then, is if the Green party splits the Labour vote.

The task for Zack Polanski’s party is huge: it has no councillors in the constituency and finished 14,000 votes behind Labour in 2024. Campaigners have had to appeal for help to store placards and posters in local sheds.

But what they lack in resources, they make up for in enthusiasm. In a windswept Morrisons car park, an army of volunteers has gathered in rainproof jackets and walking boots to deliver some of the day’s 40,000 leaflets. They have travelled from as far as Birmingham, Barnsley and Belper and by mid-afternoon all the flyers are gone.

Their candidate, the 34-year-old plumber Hannah Spencer, is approaching something like local fame. Originally from Bolton, Spencer only joined the Green party three years ago and quickly became a councillor and a rising star in the mould of the party’s new eco-populist leader.

Now she pounds the streets with her four rescue greyhounds, talking more about the cost of living, housing and crime than clean energy and carbon emissions.

Spencer is a marked contrast to the Reform UK candidate, Matt Goodwin, an academic turned GB News polemicist. Online she is billed as “Reform’s worst nightmare” and “the grafter versus the grifter”. On Thursday, Spencer took time off from the campaign to train as a plasterer while Goodwin posed for photos with Farage.

“He’s just been bussed in,” she said of Goodwin. “He’s just a TV presenter who wants to further his own career, and I’ve proved that I will work.”

Spencer, who appeared in the Guardian 13 years ago as one of the best-dressed at Glastonbury, has had to get used to the overnight attention. Social media trolls call her a “fake plumber” and erroneously claim she is married to an ultra-wealthy financier. “I wish,” she laughed. “I can’t even get a text back.”

She had to be chaperoned by a security guard this week after a “very, very angry” man shouted “fake plumber” abuse into the party’s Denton campaign centre. “I’m not allowed anywhere by myself now,” she said. “It’s surreal.”

Labour, while noting Spencer’s popularity, is adamant that only it can beat Reform. But it is clear that the Greens – who have never had an MP north of East Anglia – are now an electoral force in Labour’s back yard. And other parties are standing aside.

George Galloway’s Workers party – which polled 10% of the vote in this seat in 2024 – has encouraged its supporters to back the Greens, as has Jeremy Corbyn’s Your Party. A campaign group, the Muslim Vote, is also backing Spencer.

Sources close to Galloway said the 71-year-old former Labour MP had been ready to stand in the byelection – marking his eighth electoral contest since 2010 – but only if Andy Burnham had been selected as Labour’s candidate.

When Starmer’s allies blocked the Greater Manchester mayor from standing, Galloway was stood down and his team decided not to field a candidate after a series of meetings with Green party officials.

About 28% of the constituency identifies as Muslim, according to the latest census, but that rises to at least half of the population in two former Labour strongholds, Longsight and Levenshulme.

Lucy Powell, Labour’s deputy leader and the MP for neighbouring Manchester Central, said it was “lazy” to suggest that the pro-Palestinian Workers party vote would simply switch to the Greens.

Anger over Gaza was “not as vociferous” against Labour as it was in 2024, she said. “I went to a mosque the other day [and] I was treated like a Hollywood star. People would have just turned to turn their backs to me two years ago,” she said.

Behind his till in Mount Auto Parts, in Longsight, Ghulam Ghaus considered his most pressing issues – Gaza, inflation and local crime – then gestured outside: “Everything is shit.”

Ghaus, 73, is a local Labour party member and plans to vote for the party on 26 February out of familiarity – he knows the councillors – rather than enthusiasm. “The Green party have good policies but they’re not so well known – you only see them on election day,” he said.

Down the street, Catherine O’Connor, 66, said her friends told her to vote for Reform but she was not a fan of its hardline immigration policies. “We’re a multicultural country – we’ve got to get on with one another,” she said. “I have a lovely Asian neighbour and every Eid they bring food around. That’s really sweet and I send them a thank you card.”

O’Connor, a retired cleaner who usually votes Labour, said she would switch to the Green party this time: “That Starmer’s not much good, is he?”

Opening his front door to Spencer in Denton last week, Alf Warrender, 62, politely told her he would be voting for Reform. Why? “The Gwynnes,” he said, referring to the resigning MP and his Labour councillor wife, Allison. “We were cheated by Labour.”

Warrender, a retired transport manager, said he was a Green sympathiser but considered it a wasted vote. Reform UK was the only party that could turf out Labour, he reckoned.

“If I thought the Greens would get in, I would vote Green,” he said, taking a “Hannah the plumber” leaflet. “I’m not a fan of Reform but I’m even less of a fan of Labour.”

His wife, Jo, a charity worker, was already planning to vote for Spencer – she was “absolutely disgusted” by the Trigger Me Timbers scandal – and took a Green party poster for their front window. “We know which way it’s going in this house, don’t we?” her husband joked.

The only certainty about this election, said Ford, was that it was a “pollster’s nightmare”. “Three parties could win, and each can tell a plausible story now about how they might do it,” he said.

Back in Cafe Plus in Denton, Stogia made one final plea before being hurried off to her next event: “I want people to give me a chance. Give me a chance. I’m fighting at every level. I’m fighting the lies. I’m fighting at a national level. It feels positive but we’ve got a fight on our hands.”