It may come as a surprise, but with the exception of security, at home and abroad, on which we have profound differences of perception and likely consequence, Jeremy Corbyn and I do not disagree irrevocably on some key policies.

I make this point because the decision party members have to make in the weeks ahead should be based on a great deal more than whether they “agree with Jeremy”. It is, after all, the role of party members to participate in determining policy and for members of parliament, elected mayors and councillors to endeavour to carry that policy into practice.

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So, while I agree with the thrust of the anti-austerity stance that is the hallmark of Jeremy Corbyn and John McDonnell’s 10 months in the job, and have consistently argued that the government’s original 2015, and then revised 2019, timetable for eliminating the structural deficit was unachievable, it is not the opposition but the government that determines where we go from here.

The recent vote on to confirming the government’s previous decision to go ahead with the four Trident systems caused great controversy. It should not be the determining factor in who gets elected as Labour leader. There are, as I indicated on Radio 4’s Any Questions? in February, very good intellectual, political and practical arguments for a thoroughgoing review of what kind of defence we will need in the 2030s, which will have much more to do with cyber conflict than the traditional variety. The idea that martyrs are deterred by retaliation is highly debatable.

Facebook Twitter Pinterest Jeremy Corbyn in London on Friday … ‘So Jeremy Corbyn is in favour of equality, and tackling disadvantage and discrimination. Well, surprise, surprise. So am I.’ Photograph: Jonathan Brady/PA

And yes, have we not already determined as a party that, in one form or another, we would like to take back the rail franchises? By any other name, if you want to use an outdated term, nationalisation.

So Jeremy Corbyn is in favour of equality and tackling disadvantage and discrimination. Well, surprise, surprise. So am I and every other Labour party member that I have ever met. The problem is that the so-called rainbow coalition so favoured by the far left in the mid-80s was based on the idea that the disadvantaged, discriminated against and dispossessed would form a majority that would carry a Labour government into office.

It did not. The strategy was based on the premise that you would find a new constituency to maintain you in government once you had eliminated the rationale for those who had put you in power in the first place. The truth is that to reduce inequality and tackle discrimination, we need to create a broad alliance for those who are not “disadvantaged and discriminated against” and who, in their desire for a better life, have to be persuaded that this involves changing the lives of others for the better. In other words, mutuality and reciprocity, not the politics of envy and victimhood.

What, then, is the real challenge? This election is all about what the Labour party exists to achieve.

If, as some zealots believe, this is about Jeremy, we are finished. It is not only that the Labour party has always been a coalition, a pluralistic force with checks and balances, it is that we’ve never believed in the “supreme leader”, with all sovereignty and power given upwards to that leader and the cohort around him or her, with decisions, massive instructions and intended outcomes passed down from that leader. What the Marxist-Leninists understood as democratic centralism.

Those who see this election as about Jeremy seem to transpose their thoughts, beliefs and political contribution on to him. It is almost like the transfer of thought and will on to a screen. Whatever you want it to be, it will be.

In this surreal moment, with the capture of the Labour party by those whose raison d’etre is opposition (even to the policies of the party they lead) – enter, left-stage, Momentum – we face annihilation. Here we have the vanguard. Not, of course, the proletariat but the middle class, often educated, potentially protected from the consequences of their actions, sometimes in comfortable retirement.

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Most are not comfortable with the thuggery, intimidation – online and in person – that is so reminiscent of what some of us had to put up with in the 1980s. New politics only in the sense of the emergence of social media. Walking through lines of your spitting and shouting opponents, the vile bile of those who preached peace and display hatred with every breath – this is my memory of the mid-80s. Jeremy is not one of those and most of those following him are not, either. But, willing or otherwise, they condone and therefore carry responsibility for not taking on those forces.

But when people cry that a year ago the mass membership, and those who had joined under the previous £3 system, had spoken, they missed the point. It is not where they, or anyone else, would like to be. It is where we are now.

“We won and we will win again,” is a meaningless slogan for anyone seriously engaged in seeking political change. If the bulk of your parliamentary party cannot work with you, cannot take office under you, cannot therefore function as a meaningful opposition and party of government in waiting, you are simply a campaigning force.

I know all about campaigning. I spoke at marches with hundreds of thousands of people making their way to Trafalgar Square and elsewhere. I know what it was like in the 80s, because at that time I led one of our principal councils in endeavouring to provide a genuine alternative to Thatcherism.

Without power, we were powerless. Not in our heads, not down the pub, not in the dreams of some distant tomorrow, but in the real world in which everyone else was living.

George Orwell, a socialist, who was the scourge of Stalinist apologists, once wisely said that the problem with Marxists was that “they do not often bother to discover what is going on inside other people’s heads”.

And there is the rub. It is not wishful thinking, it is not massing numbers of supporters either inside the Labour party or entryists through Momentum. It is what’s going on out there that matters.

At the end of May, my football team competed in the playoffs for a place in this season’s Premier League. We won the battle of the terraces, 18,000 more supporters than our opponents, cheering our team to the rafters at Wembley. In the real world, the match took place on the pitch – and we lost.

This is not a self-indulgent game. This is not about what we think, how self-satisfied we feel. This is about those with voices heard, whose dreams are made reality by the Labour party achieving what its constitution sets out as its prime objective – to win.