Labour rebels just drastically increased Theresa May’s chances of keeping her job – here’s how

Chuka Umunna and Chris Leslie were emphatic at the news conference that they would not contemplate helping to make Corbyn prime minister

The more sectarian supporters of Jeremy Corbyn got what they wanted. They wanted Luciana Berger and Chuka Umunna to leave the Labour Party for the crime of wanting to leave the party.

The close circle around Corbyn himself held to the opposite view. They were worried about a breakaway party because they could see the damage it could do to their chances at the next general election. That was why the Labour leader’s response – “disappointed” – was so mild, making the point that the party’s policies were popular at the last election.

Indeed, one consequence of today’s defections is that it makes an election unlikely even if the DUP abandons Theresa May over Brexit. Umunna and Chris Leslie were emphatic at the news conference that they would not contemplate helping to make Corbyn prime minister. That means that in a future vote of no confidence in May’s government, they would refuse to force an election – and remember that in last month’s confidence vote May would have lost by one if the DUP had voted against her.

Beyond that, the effects of this breakaway are not yet clear. What was striking about its announcement was that each of the seven MPs gave a different reason for leaving, and they had neither a leader nor a grand plan for what should happen next.

For all the Corbynites’ complaining about “careerists”, what was striking about the MPs’ statements was how personal, emotional and difficult they all found it. Individually, they had all come to their own breaking point and were leaving because they couldn’t take it any more, not because they had a clear idea of what alternative they wanted.

One of the most telling comments was from Mike Gapes, for whom Corbyn’s foreign policy was the main repulsion. When asked why he hadn’t stayed and fought for what he believed inside the Labour Party, he said: “I did stay, and I did fight. There comes a point when you have to recognise the party has changed.”

The true careerists are the MPs who agree with the seven but who stay in the party because they haven’t given up on a front-bench job. There are many Labour MPs who calculate that the party is still more likely to be in government eventually than any breakaway group. They calculate, as Tony Blair did in 1981, that the “first past the post” voting system makes it hard for a social-democratic breakaway from the Labour Party to break through.

There will be lots of speculation now about who will join the seven independents. Ian Murray, the Scottish Labour MP, has already hinted that he might. Several Conservative pro-Europeans have privately threatened to leave their party if it allows a no-deal Brexit. That isn’t likely to happen in my view, but the tensions of Brexit have produced a mirror-image of Corbynite loyalty tests in the safe Tory seats held by Nick Boles, Alan Duncan and Anna Soubry.

So there may not be large numbers of additional recruits, even though everyone knows that most of the 172 Labour MPs who voted that they had no confidence in Corbyn’s leadership immediately after the 2016 referendum are still in the House of Commons. And it is equally well known that Soubry, Dominic Grieve and Kenneth Clarke have more in common with Berger and Umunna than with their fellow Conservatives in the European Research Group.

That said, seven is a significant breakaway. Before today’s announcement there was much mockery of the idea that MPs who have long been reported to be on the verge of leaving would ever have the courage to do so. But the herd of cats was finally ushered into one place, and there were more of them than expected.

John McDonnell must be kicking himself for his slip on the Today programme 10 days ago. Sent out to try to calm fears of a split, he let his true sectarianism show. He rejected the idea that Berger was being attacked by her local Labour Party because of her stand against antisemitism. “Luciana has been associated with a breakaway party or whatever and hasn’t been clear in stating she rejects that,” he said.

“My advice to Luciana is just tell people you’re not supporting a breakaway party, you’re sticking with the Labour Party, you’re not jumping ship.”

Well, she listened to his advice and acted on it.