Jeremy Corbyn is here to stay and the Labour Party is never going to look the same again

Jeremy Corbyn’s Labour opponents are resigned to him being elected leader of their party on 12 September. No one will know for sure until the votes are counted, and the Corbyn camp plays down expectations of a knockout --winning more than 50 per cent of the first preference votes of the 550,000 members, registered supporters and trade unionists taking part. “We think it will go to penalties,” said one Corbynista –a reference to the preferential voting system in which the bottom candidate drops out and the second preferences of their supporters are reallocated until one runner wins more than 50 per cent of the vote.

Yvette Cooper has made an impressive late surge, taking on Mr Corbyn head-on and making the running on the refugees crisis – a useful reminder to Labour’s electorate that oppositions can help to change government policy. But it may have come too late to halt the runaway Corbyn bandwagon. At the start of the contest, Ms Cooper and Andy Burnham looked to their right, suspecting the main threat would come from the Blairite Liz Kendall, whereas the unexpected danger man was lurking to their left.

Labour moderates’ minds are now turning to what life would be like under a Corbyn leadership. Brave but silly talk of Labour MPs ousting him within days or months is evaporating. So is the threat of a legal challenge to the election result. Although there is some evidence of limited entryism by the far left, that cannot explain why 121,000 registered supporters paid £3 to get a vote – many enthused by Mr Corbyn. “We never thought that ‘one member, one vote’ would allow the left to create a new party, but that’s what they have done,” groaned one despairing Blairite. Another said: “We thought the left was dead but they were just hibernating. We *ucked up. Now we have got to organise and fight back. We won’t walk away. We need some entryism from the right! We have to build bridges and create a new centre of gravity in the party so we can eventually appeal to centre of the country again.”

One veteran of the Social Democratic Party’s breakaway from Labour in the 1980s who later returned said today’s circumstances are “very different.” The SDP had money –from Lord Sainsbury of Turville, now funding the umbrella cross-party campaign to keep Britain in the EU—and heavyweight leaders in Roy Jenkins, Shirley Williams and David Owen. Who would lead a new social democratic party today? The SDP’s failure (narrowly) to break the mould of British politics is a deterrent, a reminder that our first-past-the-post voting system is cruel towards small parties.

Breakaways need a catalyst: for many who joined the SDP, it was Labour coming out in favour of leaving the EU. Mr Corbyn has not ruled out calling for an Out vote in the forthcoming referendum but some allies insist he would prove a more consensual leader than many expect. A key test is whether he would stamp out talk on the hard left of deselecting moderate MPs. Another would be the Shadow Cabinet he appointed. Offering Andy Burnham the job of shadow Chancellor would be a sign that he wanted the party to come together. Appointing his close ally John McDonnell to the post would be a sign that he would govern from the left for the left. It would be hard for Mr Corbyn to unite the party and, as serial rebel himself, to impose discipline on Labour MPs.

But whatever his margin of victory, Mr Corbyn would be able to claim a mandate. It would not be easy for the Blairites to become insurgents against an insurgent leader. Any early attempt to oust him would provoke a civil war. It might backfire, since he or another left-winger could be elected in a second contest with an even bigger majority.

If Labour did badly in next May's elections –for the Scottish Parliament, Welsh Assembly, London Mayor and local authorities—then the plotting against Mr Corbyn would begin in earnest. But it would be harder to remove him than many of his critics think. Although only about 20 of Labour’s 232 MPs will vote for Mr Corbyn, about half the MPs have links with unions like Unite and might be reluctant to take part in any coup.

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Mr Corbyn would have the time and space to radically change the way Labour is run. Policies would no longer be handed down as tablets of stone by the leadership; they would be passed up from the grassroots. Labour’s annual party conference, where the trade unions and party members each have 50 per cent of the votes, and its national executive committee, would enjoy real power again after being sidelined since Tony Blair became leader in 1994. “New lines of accountability” would enable the party to hold the leader, Shadow Cabinet and MPs to account.

PLS KEEP AS PAYOFF It is not certain Mr Corbyn would lead his party into the 2020 election, but he would not walk away anytime soon. His Labour critics will soon learn that shouting he is “unelectable” as prime minister would cut no ice with his followers. His mission would be to win the country round to Labour, rather than the other way round. The rules of the game would change under a Corbyn leadership, and the ripples would spread way beyond Labour's shores.