There must surely be a lesson here somewhere. As voting forms are sent out this week to an astonishing 650,000 members of the Labour party, the highest membership of a political party in memory, London mayor Sadiq Khan and Scottish Labour leader Kezia Dugdale have urged members not to vote for Jeremy Corbyn. Expect more to urge the same.

Yet if past experience is anything to go by, the more Labour’s panjandrums urge members to do one thing, the more they will simply do the other. I suspect that the vast majority of them are now heartily tired of being warned and cajoled. They didn’t ask for another leadership contest and would quite like the parliamentary party to stop bickering and backstabbing and stand with their leader rather than against him.

At this rate Labour’s general election slogan will be 'Vote Labour – so long as we approve of you'

This whole summer of silliness began shortly after Britain voted for B​rexit. This was apparently Jeremy Corbyn’s fault and not that of a fairly significant proportion of Labour voters who were likely unpersuadable. Thus began the longest attempt at political decapitation in peacetime, and which continues to rumble ruinously on. Alternatively farcical, damaging and debilitating, it is easy to wonder why hundreds of thousands of people would actually want to join a party which immediately sends their applications to a “compliance unit”, successfully blocks their imagined right to vote, and whose deputy leader in the avuncular shape of Tom Watson who believes that they are being groomed by a malign bunch of septuagenarian Trotskyists based in Crouch End.

At this rate Labour’s general election slogan will be “Vote Labour – so long as we approve of you”. It all reminds me of the former Labour whip Ray Powell when he was presiding over the old Ogmore Labour club in south Wales. Then the refrain, I was informed, was: “So you want to join the Labour party, lad? Sorry, we’re full up.” Stories such as these would have Michael Foot quoting his hero Aneurin Bevan to us in the Tribune offices: “The right wing of the Labour party”, Michael would say, “would rather see it fall into perpetual decline than abide by its democratic decisions.”

It is 10 years since I was a member of the Labour party’s national executive committee. I remember the first meeting of the NEC that I attended in the Imperial hotel in Blackpool. Alongside three other refuseniks that I had just been elected with, we were sat, squinting in front of a large window while across a table Tony Blair, joined on either side by other sepulchral silhouettes, gave us a very stern lecture about party loyalty.

To an extent that tempered how I behaved as a one-time serial rebel, albeit one who was active before the temptations of social media. Dennis Skinner, who I used to sit next to during those interminable meetings, imparted a wisdom that I tried to take on board: “don’t question the motives of others”, he would say.

That didn’t stop me from getting into scrapes, nor can I claim pure innocence of attempted subterfuge. I was involved – I think it was with the late Michael Meacher – in an attempt to work up the 50 or so MPs’ signatures needed to trigger a leadership contest against Blair after the Iraq war. That was until a furious Angela Eagle told me to take her name off the list because it shouldn’t have been on it and we all got cold feet. But I still have a letter from Cherie Blair thanking me for a later Guardian article, which condemned subsequent parliamentary coup attempt leaders for their “cowardly” attempt to dislodge her husband through an anonymous vote of no-confidence, rather than raising the 50 or so named MPs needed to mount a challenge. It is funny how history tends to repeat itself in the Labour party.

Today we have a Labour leader elected on a landslide a year ago because, like Bernie Sanders in America, his political platform represented a break with austerity and near-permanent war. His agenda – described by pollster Peter Kellner as “hard-left” over the weekend – is nothing of the sort. It more resembles a mild form of social democracy – which has had its echoes in Guardian editorials for almost as long as I have been a reader. His challenger – who is not drawn from the serried ranks of critics who have now uncharacteristically largely fallen silent, the quite likeable Owen Smith – seems to largely share it.

So what on earth is all this about?

Perhaps it is down to electability. Jeremy Corbyn, says Khan, “can’t win us the next general election.” Yet apart from Khan (who in fact did rather well by many of Corbyn’s supporters), many of those shouting loudest haven’t exactly won Labour many of those previous elections. Then there are some of the commentators, their flame-flecked fury a reflection perhaps of their irrelevance to a generation that increasingly gets it news and views from elsewhere. Others cite pollsters who haven’t managed to call an election or a referendum correctly for years. When they keep on shouting that “Corbyn can’t win a general election” their cries risk becoming a self-fulfilling prophecy.

Do I think Corbyn can win? With parliamentary boundary re-organisations, with the atrophy and collapse of Labour in Scotland, it would be bloody hard for any Labour leader to win right now, but it has to be worth a try – whoever it is. And whoever wins will have to broaden Labour’s appeal, not by the triangulations of yesteryear, but by acknowledging that political gravity is shifting away from what has gone on for the past 40 years. I also think that members and supporters are any organisation’s lifeblood, and that before Labour became a mass party of over half a million strong, it was on full life support.

But never mind the “Trots”, in today’s Labour party we will have elections until the members either get it right, or we return to the electoral college system being demanded by many of those who wanted to get rid of it in the first place in order to marginalise the unions (but still take their money). Thus ensuring that the madness of actually allowing one-member-one-vote elections that produce winners the party establishment disapproves of, would never be allowed to happen again.

Let’s hope that the parliamentary Labour party calms down, sees sense, and gets behind whoever is elected in September. In the meantime, the only advice I can offer Corbyn’s sworn enemies is to buckle down, make that banner – and march on Islington. I suspect it would have to read “Vote Corbyn” to have any chance of success.