Caroline Lucas’s plan for an all-female emergency Cabinet to stop a no-deal Brexit is a fantasy, with no prospect of success. But if the plan is daft, it has provoked a revealing reaction from Jeremy Corbyn’s loyal outriders.

Instead of laughing it off, many have taken it deadly seriously. Most have focused their attack on the ethnicity of the women Lucas chose to enlist: they were all white. Reasonably enough, they asked why shadow home secretary Diane Abbott, was overlooked. Recognising her mistake, Lucas apologised. But instead of giving Lucas – probably the most politically correct member of the Commons – the benefit of the doubt, the Corbynite response has been nasty and vituperative.

If Owen Jones merely expressed his disappointment, NEC member Lara McNeil called her that favourite Corbynite insult: a ‘melt’. Others assailed the Green MP’s ‘bigotry’. There is some genuine outrage at Abbott’s exclusion. But what underpinned this largely performative online fury was revealed by commentator and semi-professional potty-mouth Ash Sarkar when she described the Lucas Plan as an ‘attempt to fuck over Corbyn’. As the Canary editor Kerry-Anne Mendoza said, the fear was that Lucas was ‘making alliances with pro-fracking, pro-austerity, imperialist Tories & Lib Dems to keep socialists out of govt’.

This is an incredible turnabout. During the summer of 2015, when Corbyn was campaigning to become leader, Lucas said she ‘had never felt so optimistic about a potential leader of the Labour party’.

The surge in membership associated with Corbyn’s leadership was partly thanks to Green voters joining the party. This regard was reciprocated. Chris Williamson, who is one of Corbyn’s most loyal MPs, lost his marginal Derby North seat in 2015 because, he claimed, Ed Miliband had failed to attract voters from the left, most especially Greens. But in 2017, Williamson stormed back to Parliament, partly thanks to the Green party standing down in his favour. In the aftermath of that election, Williamson talked of a Green-Red alliance and his support for environmentalism. Some wondered what was the point of the Green party after two-thirds of their 2015 voters switched to Labour.

Since then, Corbyn’s mishandling of Brexit has helped the Greens recover – at Labour’s expense. If Corbyn dithered over whether he was Leave or Remain, the Greens stood proudly and loudly behind the Remain banner. As a result, they nearly doubled their vote share in the 2019 European elections to 11.8 per cent, just a few points behind Labour. If some Corbyn supporters, like the commentator Paul Mason and MP Clive Lewis still see merit in a Green-Red alliance, they are considered apostates by the Labour leader’s office.

After all, in Corbyn’s bunker, those who are not friends are enemies. Thanks to differences over Brexit, the Greens are no longer friends. To Corbyn’s keenest supporters, politics is a question of Socialism or Barbarism: a Corbyn-led transformative government, or the dark night of a neoliberalism whose only end is fascism.

The closer they have got to power, the more they feared their failure to achieve it. This delicate psychological state became even more acute after the remarkable 2017 election result brought the keys to Downing Street so tantalisingly close. And while the likelihood of Corbyn becoming prime minister has lately receded, thanks to Britain’s electoral system it is still possible. So to Corbynites, those who stand most implacably between the party and power are not the Conservatives, but ‘centrists’ – people like Tom Watson in their own party who, they believe, would rather hand the initiative to the right than build a socialist Britain.

It is a childish but powerful fantasy which dichotomises politics between the Elect and the Damned. Unfortunately for Corbynites the great political divide is currently between Leave and Remain, not Socialism and Barbarism. But in their refusal to face that reality, Corbynites have turned friends into enemies. This explains why they see the Lucas Plan, not for what it is – a desperate attempt by a well-intentioned MP to keep Britain in the EU – but as part of a dastardly conspiracy against Corbyn’s big project – a view as fantastic as the Lucas Plan itself.

Steven Fielding is professor of political history at the University of Nottingham. He is writing ‘The Labour Party: from Callaghan to Corbyn’ for Polity Press, published in 2021