I meet Momentum Hastings at a railway union picket line. It’s a cold evening, but about a dozen activists and a handful of trade unionists have turned up, dressed in red and yellow, to hand out flyers at Hastings station. Such is Southern’s reputation for dismal service as the dispute over staff levels on trains drags on, that the response from commuters is largely positive – “98% positive”, Louise, a Momentum activist, tells me, with just one man tearing up a leaflet in her face.

Trooping to the pub after exhausting the RMT leaflets, I feel hopeful. The picket seemed the sort of energetic, popular local campaign that could go some way to closing Labour’s gaping poll deficit. The picketers even get a raised fist and a chorus of “well done, brothers and sisters” from a group of punters. Not the most reliable polling data, but pretty encouraging for a Hastings Wetherspoons.

Momentum Hastings seems pleasantly free of the kind of dogmatic, acrimonious squabbles that have recently engulfed the movement at national level. “We’re not interested in moulding people into what a socialist should be,” says Tariq Persaud Parkes, one of the group’s co-founders. “We say to people: come with your ideas, and let’s have a talk and see what we can do. You might be pro-Trident or anti-Trident, pro-nationalisation or anti-nationalisation, but any view is valid.

We are not interested in moulding people into what a socialist should be ... any view is valid Tariq Persuad Parkes, Momentum Hastings

“If you start getting into complicated meetings about the structure of Momentum, the reaction here will be, ‘never mind that, I want to go and do something’,” says Kay Green, another co-founder. “If we want to do the formal stuff, we can do it in the Labour party. Momentum is a useful activist group, and we just get on with it.”

Across a number of Momentum groups, this seems to be a common thread. The idea of Momentum – put by one activist in Stockport – is that of a “force multiplier” for local single-issue campaigns and Labour electoral drives. It’s an enticing idea, and one that is at odds with most of the media coverage of Momentum, which either depicts it as a sinister organisation dedicated to purging the ranks of the parliamentary Labour party or a bastion of totalitarianism.

Labour’s dire poll ratings are the elephant in the room. Stick a microphone in a Momentum member’s face and ask about the polls, and you’ll probably hear some variant of: “Well, you can’t trust them, can you?” After Trump, Brexit and Miliband, there’s an element of truth to this, but the margins of error in those cases pale in comparison with Labour’s current deficit, which at the last count stood at 16 points.

But most accept that Labour’s rating is a serious problem. “You have to be concerned about the polls,” Anthony Hay, a Momentum Stockport activist, tells me when we meet in the local Labour club. “But also the Labour party itself has a lot to answer for. When your own party is telling the public that they’re unelectable, that’s going to have an effect.”

Momentum Stockport was founded by two longstanding Labour activists, Navendu Mishra, a former council candidate, and Charlie Stewart. Stewart, for his part, has been a Labour party member for nearly 40 years and is a local councillor. As in Hastings, the idea was to channel the enthusiasm of new members into activism.

The idea that the Labour party might go the way of the once-dominant Greek socialist party, Pasok, or France’s socialists under the leadership of François Hollande is omnipresent in Momentum, and all the stronger after the defeat of Hillary Clinton. There is no denying the threat to Labour is real. In Stockport, it comes in the form of a bullish Ukip under MEP Paul Nuttall.

Dave Kennedy, a Stockport trade unionist and supporter of Momentum, has a clear view of the problem: “We had two general elections where the model failed, and you had people saying that we had to go back to this model that keeps on losing.”

What isn’t clear, though, is how the Labour party under Jeremy Corbyn would be able to pick up on this amorphous, “anti-establishment” vote, particularly in a hostile media landscape, and divisions within the PLP and Momentum itself.

Momentum HQ’s solution is an unprecedented mobilisation of its membership, in the hope that the doorstep press can outweigh the hostility from Fleet Street. Beth Foster-Ogg is a Momentum organiser, one of those helping to bring Momentum’s 20,000 members and 170,000 supporters into local campaigns. She’s working at a phone bank in Momentum’s central offices when I meet her. Staff have been brainstorming some slightly off-the-wall merchandise ideas on a whiteboard – including what looks like Labour branded champagne (“Champagne Socialist”).

Momentum’s answer to hostile media coverage and internal divisions is to take the fight to the doorstep. Photograph: Bloomberg/Bloomberg via Getty Images

Foster-Ogg is involved in setting up an initiative called Momentum Trainers’ Network. Momentum will train a network of activists to go out to local groups and run sessions, free and on demand. “We want to upskill people in running campaigns and community organising,” she says. “Lots of people will say ‘I want to run a campaign on the NHS’ but what does that actually mean? Are you going to leaflet people? Is that effective? Lots of activists don’t know how to campaign.”

The hope is that these people will be able to change the Labour party from, as Foster-Ogg puts it, a machine focused winning elections by maximising turnout on the day, to one that entrenches itself in communities by getting involved in single-issue campaigns. That, she hopes, is how the party will reverse its poor poll showings. However, there is a catch – Momentum Trainers’ Network is currently postponed, pending resolution of the current dispute about the movement’s structure.

Three days after our meeting – last Saturday – the simmering tensions in Momentum once again burst into public view. A fractious meeting of the national committee led to a widely circulated blog post by one of Momentum’s women’s reps, accusing members of the steering committee of bullying, as well as claiming that Trotskyists were attempting to take over the movement.

In brief, the dispute is about which voting system Momentum uses – one-member-one-vote (Omov), as in the Labour leadership election, or elected delegates. Momentum’s national committee was divided, but voted by a small margin in favour of a delegate system last Saturday. Emails were leaked implying that members of hard-left groups had conspired in favour of the delegate model. The commentator Owen Jones waded in on the side of Omov, declaring that “these sectarians must be stopped”. On social media, activists traded accusations of “Stalinism” and “entryism”, as well as a bizarre, painfully ironic meme riffing on Plato’s cave that depicted supporters of the delegate model as “CIA” and “hitlers men” [sic].

I visited Momentum Hackney in early November, shortly after the dispute first spilled into the national press. As Momentum groups go, Hackney’s is known as one of the more proactive and outward-facing, running workshops for potential councillors and educating members on the structure of the Labour party.

About 35 people turned up to the public meeting. For many, it was only their first or second time – some were wearing school uniform, others were retirees. The first item, as it had to be, was about the Omov/delegate debate. The discussion was cordial enough, but most people around the circle remained silent. One man had come from a water charity, hoping to canvas Momentum’s support for a campaign he was running. He was paying for childcare, so his attendance was costing him roughly £10 an hour. Mid-debate, he raised his hand to ask, “What actually is Momentum?”

His confusion wasn’t matched by all those in attendance. An older man, dressed in a football shirt and boot-cut jeans, raised his hand. Leaning forward in his chair, he announced that he was here from the Socialist party – the successor to Militant. The delegate model, he explained, was the only way a left-wing movement could organise and survive. As a rousing end to his argument, he called on Momentum to “literally stamp on the right wing”. It didn’t get much of a reception in a room full of people mostly concerned with saving their local pathology lab. Perhaps worried that his political position might seem a bit ambiguous, he had “TROTSKY” printed on the back of his shirt.

Excessive discussions about procedure do this to a movement – distract members from proper activism. It is right that there is a debate about the future of Momentum, and it’s important that local members are involved and engaged with it. Still, the bitter and protracted nature of this split looks as though it will only alienate and drive away potential activists, many of whom have turned up because they want to campaign on a local issue, or bolster Labour’s flagging poll ratings.

One of Momentum’s strengths lies in providing an easy route into political activism for the thousands of new, enthusiastic Labour members. Activism isn’t everything – having a slick media operation helps – but at a local level, Momentum really does seem as though it could help revitalise the party. Looking at the toxic debate at the top of the movement, and the trading of bitter, loaded insults, many may want no part in it. More than that, it presents a sad contrast with some of the inclusivity and open debate at grassroots level.

Founded in 2015 by Jon Lansman, Momentum now has 150 local groups and more than 20,000 members across the UK, as well as some 170,000 supporters. The group was set up to build on the energy and optimism behind Jeremy Corbyn’s election as Labour leader - but its politics have proved controversial.

Most recently, a plan to give members an equal say on the direction of the movement was narrowly rejected at a fraught national committee meeting. The proposal was set out in response to fears that a small minority of older Trotskyist sectarians were dominating the group. Votes were split along generational lines.