Perhaps it’s the heat. On Thursday night, a hashtag started to trend on Twitter: #WeAreCorbyn. Surveying the gelatinous tributes to the Labour leader, I experienced something strange: a grudging burst of respect for the prime minister.

There are few good things to say about Theresa May, but one of them is this: she doesn’t encourage her supporters to treat her like a baby bird with a broken wing. Jeremy Corbyn, by contrast, can feel like a victim perpetually in search of an oppressor. No one doubts that he has been subject to harsh, and sometimes unfair, criticism. But so has May. And no one is posting moist-eyed memes about her saintliness.

Any political movement that demands such public displays of love for its leader should be regarded with suspicion: just think of Chairman Mao’s “loyalty dances” or the Make America Great Again mob chanting abuse at reporters covering Trump rallies. The practice restricts free debate, rebrands dissenters as enemies and dismisses any scrutiny as sabotage.

John McDonnell has signalled that he wants to do whatever is necessary to move on

It’s tempting to treat Twitter as irrelevant: a digital Versailles, filled with bored media and political aristocrats getting on each other’s nerves. But Twitter is where the glimpses of the Corbyn-supporting ecosystem of blogs and Facebook groups break through to the surface, so it is vital to understanding why the Labour leadership has been so tone-deaf to Jewish concerns.

Spending any time there makes it clear that there are still many Corbyn supporters who believe the antisemitism row is not only being pushed by his enemies – a reasonable claim, given the Tories’ hypocritical interest in it while ignoring their own problem with Islamophobia – but manufactured entirely to discredit him. Such kneejerk defensiveness is poisoning the left, condemning it to endless infighting and restricting its ability to fight the Conservatives. If politics is reduced to Jeremy’s Army – are you in or out? – even those with cast-iron Corbynite credentials cannot get a hearing when they disagree with their leader.

Take the example of Momentum, a grassroots organisation entirely dedicated to advancing the cause of leftwing politics and one with a huge amount of personal loyalty to Corbyn himself. On Wednesday, it withdrew its support from Peter Willsman, one of its candidates for the party’s national executive committee. Audio had emerged of Willsman questioning whether there really was “severe and widespread” antisemitism in Labour and rejecting the concerns of 68 rabbis who wrote an open letter to the party. (As a member of the party’s disputes committee, Willsman will have heard evidence of members expelled and suspended for antisemitic comments, making this hard to believe.) He did this at a meeting where Corbyn was present.

Peter Willsman questioned whether there was actually ‘severe and widespread’ antisemitism in the Labour party. Photograph: ITV

The NEC elections are important because the committee oversees Labour’s rule book, selection and disciplinary processes. (Want to bring back deselection? You need the NEC on board. Want to reduce MPs’ influence in the party relative to members? One for the NEC.) Momentum’s slate – originally called the “JC9” – is expected to win handsomely, thanks to its administrative muscle. But Willsman, chair of the Bennite Campaign for Labour Party Democracy, might now lose his place.

That would make no difference to the overall numbers – Corbyn still has a solid majority for whatever reforms he wants to propose. But the political significance of the (almost) decimation of the JC9 is that it represents the beginnings of a fissure between the leader’s office and Momentum. In ditching Willsman, the grassroots group has shown it is willing to take unpopular decisions in order to demonstrate that the concerns of the Jewish community have been heard. Notably, Momentum’s founder and director, Jon Lansman, backed the move in defiance of key players inside the leader’s office.

This matters in terms of Labour’s future. Forget Blairites (or whatever the current insult is) versus Corbynites – that war is over and Corbyn won it. All the action now in Labour is left on left and not just on this issue. Why did Labour offer a free vote on a third runway at Heathrow? Because John McDonnell’s constituency is nearby and he is implacably opposed to the idea, while Len McCluskey’s Unite praises the “jobs, economic prosperity, investment and 10,000 apprenticeships” it would bring. Faced with a split between these two power-brokers, Corbyn reached for May’s favourite political substance – fudge.

In the antisemitism row, the fractures are more complicated. A few reliably pro-Corbyn commentators broke from the leadership line once the audio was released. Throughout the saga, Momentum’s Lansman has been circumspect in public but has lobbied for a tougher line in private. And McDonnell has signalled that he wants to do whatever is necessary to move on. In both moral and tactical terms, he is right: his pledge to include a universal basic income trial in the next Labour manifesto was buried under bad headlines about Hamas. Outside the #WeAreCorbyn hardcore, there is a general inability to understand why Corbyn is so unwilling to yield any ground.

The shadow chancellor, John McDonnell. Photograph: Aaron Chown/PA

Set against that, the instincts of “Loto” – the office of the leader of the opposition – are to hope the row will go away on its own. Corbyn’s latest op-ed was a damp squib. It copied and pasted paragraphs from a piece he wrote in April, did not offer to adopt the full International Holocaust Remembrance Alliance examples of antisemitism and was released on the non-Shabbat-friendly time of Friday evening. Yes, antisemitism exists, he conceded, but it was nothing to do with him; he is a lifelong anti-racist campaigner, after all. It was the verbal equivalent of an early day motion, positioning him on the side of the angels while accomplishing nothing of substance.

Allies of Corbyn are realising that the stubbornness that led him to oppose apartheid and the Iraq war when those were marginalised opinions also means he is unwilling to listen to them on other subjects. As a backbench campaigner, his rigid, unyielding style was widely admired. As the leader of the opposition, and a possible future prime minister, it feels like a liability. Every budget, every policy, every decision creates losers as well as winners. Can he be honest about that? And can his most ardent supporters acknowledge that perfection is impossible?

The political instincts revealed by this row should worry Corbyn’s supporters – as well as anyone who wants a successful leftwing government to replace Theresa May’s no-hopers. By the next election, the condition of Britain might well be appalling. Brexit is sucking all the political oxygen out of the room and Whitehall has little energy left to address anything else, even as the public realm creaks and crumbles.

There is no shortage of attack lines ready to be deployed by an effective opposition. Northamptonshire council is effectively bust, thanks in part to the “devolved axe” of austerity. Universal credit has received another stinging report, this time pointing out that – just as opposition MPs warned from the start – paying benefits to a household rather than individuals makes it harder for women to leave abusive partners. Chris Grayling’s ministerial reign of terror continues. We can see it in the chaos of the rail network in the north of England and in the £170m lost because botched private probation contracts will have to be ended early. And that’s before we even get to the fact that ministers are now suggesting that stockpiling Spam is a small price to pay for the ability to strike a trade deal with New Zealand.

It’s therapeutic but pointless to blame the media for covering antisemitism instead of these concerns. Opposition leaders always struggle to be heard – and it doesn’t get much easier when you’re in power. It’s why the Blair era prized “message discipline”, repetitive soundbites and “the grid”. (Only dictators get hours of fawning coverage from state television to outline their grand ideas and pet theories. Everyone else has to fight tooth and claw for any coverage at all.) It’s why pollster Philip Gould advised that the party should sometimes “concede and move on”.

Yes, Corbyn’s unwavering commitment to the causes he believes in has always been one of his most admirable traits. But the question has to be: why is alienating British Jews one of those causes?

Helen Lewis is associate editor of the New Statesman