There are a lot of people who at some point supported Jeremy Corbyn, but are now saying ‘with a heavy heart’ – always with a heavy heart – that he has to go. I would like to ask them to think one more time about this: to ask themselves why they supported him in the first place, and what has changed.

Most of the Parliamentary Labour Party hate Corbyn. More than that, they hate what he stands for. When they claim to think he’s a nice guy, they may well be telling the truth. What they can’t tolerate is the possibility of a real challenge to the continuation of the Thatcherite and then Blairite politics which blights the lives of the vast majority of people. Until recently – for my generation, FOR OUR ENTIRE LIVES – there has been no hint whatever of a parliamentary alternative or even a meaningful challenge to this politics.

When the challenge finally came, some people who had always claimed to be horrified by the status quo, and had stressed the need to work to challenge it from within the system, found reasons not to support it: people wouldn’t vote for it, or not yet; it would split the party; it would give the Tories yet another term in power. But others, perhaps after much hesitation and soul-searching, decided to back Corbyn. The anti-austerity politics that he stood for was overwhelmingly popular among Labour members and supporters. The Parliamentary Labour Party tried everything to stop him, and to discredit the movement behind him. Slightly more sophisticated critics maintained that they personally would love to see Corbyn succeed, but the nasty PLP and the nasty media would crucify him, and his current mass support would wither away; we needed someone who would be found acceptable by the nasty PLP and the nasty media; hence, we needed someone with nasty politics – but Corbyn’s supporters could hear the screams of the baby being thrown out with the bathwater.

What has happened since then to change people’s minds about Corbyn and make their hearts heavy? Did he sell out, compromise his anti-austerity message, or start pandering to racist anti-immigration sentiment to make himself ‘electable’ (like the Labour Party in May 2015, or the people Corbyn beat in the leadership contest)? Did he give up on the whole integrity thing, and pretend that he’d always loved the European Union and its pro-market, pro-austerity politics more than life itself?

What has happened is a referendum victory for Brexit, not because of Corbyn or Momentum – who, unlike the Leave campaign, did not pretend the EU was responsible for starving the NHS – but because Conservative and New Labour politicians spent decades making people’s lives worse, then insinuating that it was the fault of brown people, Muslims and Eastern Europeans, until David Cameron decided to try to get his frenemies off his back for a bit by giving them what they wanted and making people vote on something almost nobody understands, then trying to persuade them to vote the right way by telling them how well their lives are going as things are and how bright their futures will be if they stick with him. Which didn't ring very true.

The EU has nothing much to do with immigration, but that didn't matter. The referendum result had little to do with Corbyn, but that doesn't matter either. The PLP have seen their chance to move against him.

What else? There may be a general election sooner than we thought. People who want the Tories out are worried they might win again. And some of them seem to think that the way to stop that is to withdraw their support for the leader of the opposition, just before an election, and replace him with … someone. They are confident that whoever this someone is, (s)he will be better at winning votes than Jeremy Corbyn, even though he isn’t at all bad at winning votes, especially just after people have said he can’t win. Their maturity and good sense tells them that enough is enough. ‘New!’ they say. ‘New, new! Out with the old new and in with the new new!’ – never mind that it looks a lot like the same old same old.

This isn’t maturity, or realism, or courage. Realism now means sticking with what we’ve got, at least for more than ten months. It means remembering why we ended up here in the first place, and resisting the temptation to find reasons to wander off, you and your heavy heart. Because, right now, it is Corbyn’s Labour or nothing.