Should it be Yvette, or should it be Chuka? Or maybe Keir Starmer? Lisa Nandy? If none of them dislodge Jeremy, there’s the nascent new centre-left party, preparations well under way. This was the talk at some Labour gatherings to watch the election right up until 10pm last Thursday when the exit poll landed. Now all leadership bids have been quietly shelved, and the only real questions for Labour moderates are whether they want to, and whether they will be asked to, rejoin the shadow cabinet.

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Jeremy Corbyn has pulled off one of the most remarkable – and to many people surprising – achievements in the history of modern British politics. The next question is whether he has it in him to pull off a second, even bigger, achievement.

The first achievement is obvious, and now acknowledged even by some of his most vociferous and vituperative internal party critics. He energised an entire generation around a traditional leftwing manifesto; persuaded them to actually go and vote; and by doing so completely upended the prejudices of the political class, the pollsters, and Blairite Labour opinion. This is his victory and – despite the help of Momentum – in effect his alone.

Even by some natural admirers he is seen as an almost accidental Labour leader, an affable and unworldly character unable to dissemble or to effectively plot. But this is yet another underestimation. If you look at Labour’s policy on the police, Trident and the monarchy, Corbyn has proved well able to put his own convictions to one side in the greater political interests of the Labour movement.

Corbyn called Labour’s manifesto the star of the campaign, and he was right. He’s emphasised how much it was the product of collective conversations inside the party and among affiliated organisations. As he said it, that sounded a slightly dull idea. But what he was really saying was that he and everybody else had compromised in order to get the best, most engaging political agenda possible.

It was certainly that. Although by the neoliberal standards of contemporary Britain it was regarded as wildly leftwing, in fact it was a manifesto that almost no traditional Labour leader would have flinched at. Nationalisation? Tick. A bit of relatively modest redistribution? Tick. Equality-of-opportunity policies, particularly aimed at children, the young and the elderly? Again, tick. Wonderfully, a pledge on one of my great bugbears – hospital parking charges. Tick.

This was a manifesto that allowed many Labour candidates who are no fans of Corbyn to honestly and unapologetically campaign for a Labour victory. That, as much as engaging the youth vote, was his tactical victory.

So what is the second achievement he could pull off? Let me paint a picture of the Labour party in a year’s time. Corbyn is the leader. John McDonnell remains as shadow chancellor. But Yvette Cooper is home secretary; and Chuka Umunna, Angela Eagle, Hillary Benn and Rachel Reeves all have key jobs.

The Labour party’s long civil war is over. Almost all Corbyn’s critics have openly and frankly acknowledged his qualities and his success, (Peter Mandelson and Owen Smith were among the first to do so). Elements of the manifesto that still made middle Britain nervous, in particular the highly ambitious borrowing and spending projects, have been modified and endorsed by impeccable outside experts. That almost impossible marriage of radicalism and reassurance has been achieved.

Let me continue the picture: the Labour party of 2018 is well able – unlike that of 2017 – to gouge out Tory redoubts across the Midlands and the north of England, sufficient to give Corbyn a big workable parliamentary majority. It is Labour United, the final nemesis of Tory neoliberal and nationalistic extremism. And it is not impossible. It would turn Corbyn from an incendiary rebel Labour leader – a leader who achieved the kind of surge in support that only Clement Attlee had managed before – to Corbyn, the radical Labour prime minister.

So what is needed to get there? Corbyn has already opened the door, saying: “Of course you have got to reach out.” But the first thing for the Labour moderates is, frankly, surrender. There is a vast amount of talent that has been squandered in a futile revolt against Corbyn. Now there is a lot of humble pie to be eaten: once senior figures must not assume they have a God-given right to saunter back into central shadow cabinet positions. Most will have to work their way back from more junior roles.

And it gets worse: the rebels would have to acknowledge that the Labour left has the right to continue to own most of the policy agenda; and they must vigorously support that agenda. There will be arguments and discussions around what is practically and economically possible; but the whole neo-privatisation and market-mimicking agenda of the Blairite years must be consigned to the dustbin of history.

Corbyn 2.0 now has to go further, reaching into angry, sceptical, middle-aged electorates around the country

From the point of view of the left, none of this will be terribly easy either. In due course loyal Corbynites, who did the decent thing and stuck by the leader when others fled, may have to be demoted. There will be compromises over policy. And many will say: Why bother? Why give an inch to those sods who tried to destroy Jeremy at every opportunity?

But the answer is: because Labour needs to win, and to win much bigger than it did even in that extraordinary election of June 2017. Corbyn’s Labour has done a remarkable thing. It has reached out and brought in hundreds of thousands of younger and excluded voters who the smug political class thought were beyond reach.

But Corbyn 2.0 now has to go further, reaching into angry, sceptical, middle-aged electorates around the country who know the price of everything. Corbyn’s party needs to give the tree another shake, but much harder. Labour now has to sound like a government in waiting.

The most dangerous thing in politics is to get carried away by your own success, and therefore to stop making difficult changes. Theresa May went into her disastrous election because she believed her own propaganda. She became a frozen, smug leader, who was no longer really listening. Jeremy Corbyn, justifiably delighted by his success, mustn’t do the same.