Jeremy Corbyn has had his moment – if he truly cares about the people he’ll step down now

When the demigod of Glastonburys past can no longer fill a yurt, it’s more than a wake-up call. It’s a klaxon call through amplifiers turned up to 11 to get off the main stage

What seriously threatens Corbyn’s beliefs is him remaining to fight for them (PA)

I was going to pre-empt what follows by placing it under the header of fantasy politics. But since every aspect of our politics feels rooted in fantasy, and not the good kind, that is far too indistinct.

So file it under the label of idealistic politics when I raise the possibility of Jeremy Corbyn standing aside to let a comrade lead Labour into the next election.

The caveat about opinion polls is familiar, and they could be mistaken yet again. Even if not, the figures might shift during a campaign held at a moment of extreme volatility.

But the numbers are so abysmal that anticipating anything but a tragic outcome for Labour has become an article of faith. And faith in Corbyn has dwindled close to invisibility.

Hearing a snatch of “Seven Nation Army” during this morning’s rugby semi-final in Japan was a poignant reminder that you never hear “Oh-ohhh Jeremy Corbyn” any more. At the anti-Brexit rally in Parliament Square eight days ago, the chant was amended to a scornful “Where’s Jeremy Corbyn?”

The “absolute boy” has vanished beneath a foaming tide of dither and confusion. He has lost the dressing room in the guise of his most senior colleagues.

Most disturbingly, he has lost those who deified him in 2017. If ever a poll struck mortal dread into those who share his values, and are nauseated by the thought of a majority Tory government, it was the finding that voters aged 18-24 prefer Boris Johnson.

Why they do so – Johnson’s alleged star power, or the drip-drip-drip of dementedly hostile media coverage of Corbyn, or a sense of Brextrayal – may intrigue academic psephologists. But what matters is the fact. A demographic that has favoured Labour by enormous margins for decades no longer prefers it at all.

Almost every other poll is mortifying. His negative approval ratings are unprecedented. In London the Tories lead. A national survey released today has them on 40 per cent, 16 ahead of Labour (and one ahead of Labour and the Lib Dems combined).

But it’s that yoof statistic that liquefies the bowels. When the demigod of Glastonburys past can no longer fill a yurt, it’s more than a wake-up call. It’s a klaxon call through amplifiers turned up to 11 to get off the main stage.

Over the years, the likes of me have written the same about other terminal liabilities to their movements and most cherished beliefs.

It was bludgeoningly obvious that the Gordon Brown of 2009 and post-tuition fees Nick Clegg were destined, if they stayed, to become the enablers of policies that were anathema to them.

If Brown had resigned in 2009, and Clegg in 2014, there is every chance that austerity and Brexit would have been avoided.

Yet of all the pieces of advice offered by Clint Eastwood, the last one the generic frontline politician is psychologically capable of taking is Dirty Harry’s “A man’s gotta know his limitations”.

Not for more than half a century has an Anglo-American leader fallen on his sword in this context. The young voters on whom Democratic candidates depend had turned against Lyndon Johnson over Vietnam, and were chanting “Hey, hey, LBJ, how many kids did you kill today?”. His approval numbers were sub-Trumpian. Accepting he was a fatal liability, he declined to run for the nomination.

In the event Richard Nixon beat Hubert Humphrey in 1968, primarily with racist wolf-whistling (ring any bells?). But it was only by a whisker in the popular vote, and had Bobby Kennedy lived the Democrats might well have held the White House.

An arch political realist recognised that he was electoral poison to his party, and so almost saved it from a defeat that shaped his country (and the world) immeasurably for the worse.

One can admire Corbyn in many ways, as I do, without regarding him as an arch realist. If he isn’t a stubborn fantasist, he is an idealist. He has convictions for which he has fought, until recently from the wilderness, since not long after LBJ rammed the Civil Rights Act through congress.

You needn’t be a close student of the law of unintended consequences to sense that what seriously threatens those beliefs is him remaining to fight for them.

The familiar objection to replacing a leader this close to an election is the absence of a natural successor. In this case, John McDonnell is oven ready.

I appreciate McDonnell’s insistence that the next Labour leader must be female, but this is an epic national emergency. We are weeks from an election highly likely to saddle us with five years of a possibly sociopathic rogue, his cabinet confederacy of dunces, and a more brutal Brexit than this country can bear.

All the values for which Corbyn has struggled his entire life are in graver danger than ever before. He is on the precipice of unwittingly ushering in an era of unparalleled horror for the poor, vulnerable and dispossessed. He is on the brink of handing an elective dictatorship to a charlatan to whose myriad obscenities may be added an alleged intent to rig the system by suppressing millions of votes.

Decisiveness has not been the defining hallmark of Corbyn’s leadership. But there is one decision left to him that could redeem his legacy and give Labour a fighting chance. If it seems fantastical or idealistic to expect an act of self-sacrifice, it only seems that way. It is the only realistic choice he has left.