One thing all of Labour’s factions can agree on is that Jeremy Corbyn faced a tricky dilemma over Brexit. While two-thirds of Labour voters backed Remain, around seven in ten Labour constituencies voted Leave. While a great many of his support base and new party members – urban dwellers, young people, middle-class professionals, people with degrees – are pro-EU, the majority of Labour MPs represent constituents who are in favour of Brexit.

In some ways, Brexit is a bit like a reverse Jeremy Corbyn: popular with the electorate and Labour voters at large, but unpopular with the membership.

Either way, he was going to disappoint some Labour members. So how has his decision to whip his MPs to vote through Article 50, triggering a “Tory Brexit” with none of Labour’s amendments getting through, affected his popularity?

What do we know so far?

My colleague Stephen revealed early this month that the party had lost 7,000 members over Article 50. With no internal party polling available, and without the party publishing the breakdown of members per constituency, this is the strongest evidence yet that a significant number of people are disappointed by Corbyn’s decision. I also hear from a Momentum source that there are “certainly a few thousand” of those who originally voted for Corbyn who have stopped supporting him due to Article 50.

But to put this in context, Corbyn won the last leadership election by 119,980 votes overall, and by 51,256 among members – so a few thousand leaving the party doesn’t suggest a huge exodus, especially considering the number of people he inspired to join in the first place.

The Corbynite/Remainer overlap

There is a general assumption that all the people who voted for Corbyn are bearded young men doing degrees in London, who are unanimously devastated about Britain leaving the European Union. It’s a lazy view that lumps all Corbyn voters in one category – the sort of Trendy Nu-Socialist wave that took him to victory.

There may be a sliver of truth in this stereotype, but it’s important – as pointed out in this week’s New Statesman podcast – to distinguish between “the Corbynite core” and “the swing Labour member” (who voted Corbyn in 2015 and 2016 but doesn’t have an allegiance to the party’s hard left).

From speaking to party insiders, Corbyn supporters and Momentum sources, the sense is that the prevailing opinion among the less tribal general supporters is that Corbyn’s Brexit decision is disappointing.

There is a waning of enthusiasm among these voters, who would likely support a different candidate or not vote at all in the event of another leadership election. Thousands of these aren’t members – many paid £3 to sign up to vote the first time round.

“I originally supported him because I thought he was a breath of fresh air,” one of these, a 26-year-old professional who lives in London, tells me. “It has become pretty clear that no matter how good his ideas might be, he is completely ineffectual as a leader . . . you have to be able to make them happen, whether that’s by pressuring the current government to adopt them or by showing that you can be elected. Corbyn doesn't seem to be able to do either.”

The campaign that made Corbyn leader in 2015 and partly fuelled the founding of Momentum is made up of people who now put their Remain stance above their enthusiasm for Corbyn. “The people it [his Article 50 decision] will have affected are younger people who are very pro-Remain,” a Momentum source tells me. “A lot of them are kind of like ex-Greens, or from the anti-war or anti-austerity movement, not hardened socialists – that demographic is very, very, very pro-EU, whereas Jeremy’s not really.”

And it’s not just young people. Rachel Garrick, a Labour activist and founder of the Medway Momentum branch, formerly vice chair of Rochester & Strood Labour party, believes her age group have become disillusioned with Corbyn.

“Lots of people who are my age in my friendship peer group joined up to support Corbyn – some were quite disappointed when I said in the last leadership contest I actually thought Owen Smith was the way to go,” says Garrick, who has since left Momentum and is standing for council in Monmouthshire.

“And as a result of the Brexit vote, [they] have turned in their membership cards. I’m 41, so I’m talking the Generation Xers who haven’t experienced anything but the European project. That’s what we’ve grown up in; that’s what we know.”

Online signs

There are hints online that the evangelical enthusiasm for Corbyn, which took him to two thumping leadership election triumphs, has a ceiling. Even looking at the New Statesman’s web stats, articles defending his decisions or praising him no longer seem to receive the same approval or readership on social media as they used to – and certainly his champions are not as vocal online as they were a few months ago when stories were published criticising his leadership.

Measuring enthusiasm in tweets and shares isn’t the most accurate science, but let’s not forget that the lefty social media echo chamber was a pretty good measure for how well Corbyn was going to do in the two leadership elections he has fought.

“I have noticed a dropping-off of the typical people who often reply very positively, who now have changed from backing a lot of the pro-Corbyn voices, or the pro-Corbyn sites,” says Liam Young, a writer who has written positively about the Labour leader from the start on the Independent and New Statesman. “[They are] moving much more towards to the typical Labour centre, abandoning Corbyn.”

He adds: “The opposition to Corbyn that already existed [online] has kind of ramped up as well. I think a lot of people, Remain-minded people . . . have kind of ramped up a bit and there seem to be a lot more of them as well.”

Young believes the appetite for a Corbyn champion in the media “might be dipping somewhat – I don’t think the gap now is for a pro-Corbyn voice,” he tells me.

But he would still win

Regardless of the mainstream opinion being one of disappointment or loss of enthusiasm, most people on all sides who I speak to believe Corbyn would win another Labour leadership contest tomorrow – particularly if he had a centrist opponent.

There is a view among activists, even those who are disappointed in Corbyn, that the left will always rally around Corbyn at least until a Corbynite successor is secured. Momentum is seen by insiders as a “standing army”, with the infrastructure ready to run and win another leadership election whenever necessary.

It is also thought that the second leadership election, against Owen Smith last year, “hardened” some supporters factionally in favour of Corbyn, who might otherwise now be disillusioned with their chosen leader. The Corbyn versus Smith contest – which came after the former’s lacklustre campaigning ahead of the EU referendum – is seen as the test of whether Corbyn’s euroscepticism is enough to give him the boot by the generally pro-EU Labour selectorate. It was a test he passed.

“Sure, they’re [new Corbynite members] not as vocal anymore and you don’t hear much from them at the moment,” a Corbynsceptic official at a very pro-Remain London CLP tells me. “But they never used to turn up [to CLP meetings] anyway. What they will do is turn up and vote for him. I think it’s overplayed that he’s losing his popularity [over Article 50].”

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So Corbyn’s wider support has waned, but he would probably hold onto the leadership in spite of this. This doesn’t mean, however, that he will be leader for the foreseeable future.

While the hard left and Momentum figures would still try and keep him in power if he were challenged by another faction of the party, many have become critical supporters of Corbyn (something that didn’t seem to exist at least before Brexit). There is a tendency now to characterise him as a symptom of a new politics, rather than a cause, or the catalyst to be taking it forward. “Everybody recognised from the beginning that Corbyn won’t be forever,” says an insider who was involved in Corbyn’s leadership campaign.

As former frontbencher and ally Clive Lewis MP told me last year: “What’s happened in my party in the last year or so, it’s so often focused on Jeremy Corbyn. But actually, he’s the surfer, not the wave. And it’s the wave that’s really important.”