Throughout the rebellion against Jeremy Corbyn, there was intermittent speculation that the man himself wanted out. “JC was five minutes away from resigning,” I was told of the Labour leader’s mood after PMQs on 29 June. “But Seumas [Milne, his director of communications] torpedoed the discussions.” By the time the deputy leader, Tom Watson, eventually secured time alone with Corbyn for 20 minutes on 4 July, the latter said that he had no intention of departing.

In September 2006, it took just 17 Labour MPs to force Tony Blair to announce a date for his resignation. More than ten times that number have declared that they have no confidence in Corbyn. They have been joined by every living former party leader, Labour's MEPs, 500 councillors and an increasing number of activists (according to a YouGov poll). Blair endured the resignation of seven junior government members, including Watson. Corbyn has suffered 65 frontbench departures.

Yet unlike Blair, who capitulated after two days, the Labour leader has not yielded. Corbyn is characterised as a hostage held in place by the triumvirate of his shadow chancellor, John McDonnell, Milne and Karie Murphy, the director of the leader’s office and a confidante of Unite’s general secretary Len McCluskey.

For a man who did not originally want the job (“Now we need to make sure I don’t win,” he told a supporter after he made the ballot in 2015), Corbyn has shown remarkable resilience. Allies say he is sustained by a feeling of obligation to those who voted for him as well as his ideological conviction. A shadow cabinet member spoke of a “wall of support . . . and McDonnell’s hand” preventing a retreat. Should Corbyn face a leadership challenge (and achieve a place on the ballot), his advocates are confident that he will win again. “Though it will be close,” a senior ally added.

The same YouGov poll that found 54 per cent of Labour members wanted Corbyn to resign before the next general election (and to do so immediately in the case of 44 per cent) also showed him beating the putative challenger Angela Eagle by 50-40. When registered supporters are added, his position could be further strengthened. Momentum, the activist group, said it had doubled its membership to 12,000 and received £11,000 per day in donations.

“What you’ve seen is a reinvigoration of the movement that grew last summer,” James Schneider, Momentum’s national organiser, told me. Rather than an ideological split, the divide is characterised as one between the “old politics” of Westminster and the “new politics” of activism. “A corridor coup, trying to prevent a vote, not being able to agree a candidate . . . It clarifies things for a lot of people,” Schneider said. “If your coup hasn’t succeeded in 48 hours, you’d better sue for peace pretty quickly.”

Yet afterwards, Corbyn’s opponents are hopeful that they can prevail. They speak of harnessing the energy of “the 48 per cent” who voted for the UK to remain in the EU and have been politicised by defeat. An unpublished poll by GQR found that 10 per cent of the public would pay £3 to participate in a leadership election. A plurality of this group oppose Corbyn and consist of three segments: liberal cosmopolitans, “old right” Labour and “pure democrats” who want “a strong opposition”. Rather than being disheartened by polls showing Corbyn ahead, the rebels were cheered that opinion seemed to be shifting even before a contest has begun. They will seek to overcome ­activists’ traditional loyalty to the leader by counterposing loyalty to the party. The contest will be framed as a referendum on Labour’s very survival.

But as MPs contemplate the possibility of Corbyn’s re-election, the hitherto heretical option of a split is being discussed. In its moderate form, this would involve a “unilateral declaration of independence” by the Parliamentary Labour Party and the appointment of an alternative leader. A more radical version would entail an SDP-style breakaway. An increasingly promiscuous electorate, a pool of willing donors and “the 48 per cent” who voted remain are cited in favour of this path. Were they denied the “Labour” name, the rebels could adopt a variant (eight already legally exist).

Support for this course among MPs remains slight. Most echo Neil Kinnock’s cry at the PLP meeting on 4 July: “I’m not leaving this party, it’s our party!” John Spellar MP, a veteran of Labour’s 1980s strife, told me: “Even if anybody was demented enough to do it, it would be a splinter rather than a split.” But Corbyn’s opponents claim his leadership has united previously disparate factions. “There is no animosity between those who took positions and tried to work on the inside and those who didn’t,” one told me. “There is a real sense of unity within the parliamentary party.”

The rebel MPs believe that a narrow defeat would give them a platform for repeated challenges to Corbyn. One spoke of having Watson, who has declined to stand against his leader, “in reserve”. MPs continue to fear an early general election and doubt Conservative protestations to the contrary. Having swerved the question of electability last year, Corbyn will be repeatedly challenged on whether he is prepared for this prospect.

In the 1980s, the “soft left” determined the party’s fate after the SDP split. As Labour endures a comparable convulsion today, that faction will do so again. Most of those who voted for Corbyn in 2015 were not, as former cabinet minister Peter Hain told me, “closet Trots or wild-eyed leftists”. Rather, they were “sick of vacuous, valueless politics”. But it is exactly this model that Corbyn’s allies say the “corridor coup” against him exemplified. They are confident that their opponents will suffer a second defeat – because they believe they have not learned the lessons of the first.