Change has a texture, a crackle, a countenance all of it own: it is unmistakable. Last July, at Elland Road in Leeds, I moderated one of the Labour party’s leadership and deputy leadership hustings – a job that entailed little more than calling the meeting to order, accurate timekeeping and a few other tasks related to “compliance”.

For the rest of the time I was free to observe the party’s rank and file as they made their support for Jeremy Corbyn almost embarrassingly clear. Yvette Cooper, Andy Burnham or Liz Kendall could have turned water into wine, healed the sick and secured promotion for Leeds United. Psychologically, the deal was already done. Labour had collectively and irrevocably decided that it had had its fill of clones in suits and wanted a leader who was proud of his socialism, loved the unions and preferred rallies to PMQs.

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The leadership contest was one of the first set-piece battles of the party’s civil war – a conflict that became more or less inevitable in September 2006, when Tony Blair was forced to announce his departure. Labour has since been engaged in an internal struggle of varying intensity over its future trajectory.

The publication of Margaret Beckett’s report on the 2015 general election triggered another skirmish. According to Deborah Mattinson, the founder director of the research and strategy consultancy BritainThinks, the investigation was a “whitewash” and a “massive missed opportunity”.

Although Beckett addresses Labour’s “failure to build trust in the economy”, she attributes this primarily to “the myth that we were responsible for the financial crash”. This is scarcely the point, counters Mattinson. Justly or otherwise, voters blamed the party for the 2008 financial crisis and Labour did not address the problem with sufficient urgency. Electoral politics is rarely fair. What matters is how parties respond to the hand they are dealt.

As the local, mayoral, Scottish and Welsh elections draw closer, Corbyn’s team is reportedly massaging expectations downward. Labour is apparently on course to lose all its remaining constituency seats at Holyrood, and control of 16 or more councils in England. Failure of this magnitude would naturally be a considerable threat to Corbyn’s authority, further evidence (his opponents in the Parliamentary Labour party would say) that he and his ideological brand are political polonium.

Yet Labour’s real problem is not its left, but its moderate wing. (To anticipate challenges to my provocative terminology: those whom I would describe as Labour “moderates” have little in common with the old Labour right – Jim Callaghan, David Owen, John Smith – and are scarcely rightwing in the sense that, say, Nigel Farage or Owen Paterson clearly are. Nor do I think it advances the conversation to label everyone who disagrees with Corbyn as a Tory.)

Facebook Twitter Pinterest ‘In less than a year, Corbyn has transformed a party of government that believed it would win last May into a rainbow coalition of single-issue campaigns and grassroots activism. It is, objectively speaking, a remarkable achievement.’ Photograph: Justin Tallis/AFP/Getty

The Labour left is functioning as it is meant to. It has hugely increased the party membership. It is acting in concert with the unions and peace movement. It pursues extra-parliamentary action with more enthusiasm than the bourgeois frippery of Westminster. It advances the cause of unilateral nuclear disarmament, proposes power-sharing in the Falklands and distances itself from the Atlanticism of Blair.

This is what the left does. In less than a year, Corbyn has transformed a party of government that believed it would win last May into a rainbow coalition of single-issue campaigns and grassroots activism. It is, objectively speaking, a remarkable achievement.

It is New Labour, or what remains of it, that needs to admit its faults, dismantle itself and rebuild from scratch. As the Tories found after 18 years in office, power can be a monkey on your back. You assume that the way you prevailed then – four general elections in a row, in the Conservatives’ case – will help you prevail now. It took the Tory party a long time after 1997 to realise that the electoral formulas of the past would not work in radically changed circumstances.

In the same spirit, it is worth remembering that Blair won his first landslide almost 20 years ago. No recipe for electoral victory and progressive government can last more than a couple of decades, for the simple reason that the national and global context changes so much. Last year the Tories grasped the dominant sense of insecurity spawned by the pace of technological, economic and social change. Labour did not have a coherent answer to this anxiety. And so – as much as they were weary of Tory austerity – the voters stuck with what they saw as the safe option.

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What Labour’s moderates have yet to do is move on from New Labour. Occasionally, there are signs of activity: in December Tristram Hunt delivered a strong speech on precisely this theme, recognising that “somewhere during Ed Miliband’s leadership we stopped challenging ourselves”, and that “every Labour generation needs to explain afresh why the struggle against inequality is core to our political purpose”.

In all candour, New Labour had next to nothing to say on this subject – the grotesque gap between the affluent and the poor – and its children must acknowledge as much. Nor did it have an answer to the phenomenon of “anti-politics”, the loathing of spin and the Westminster bubble. In the end, New Labour became symbolic of democratic failure rather than of government for the many not the few.

In politics, it is always pointless to relitigate the past. The voters are never going to believe that Labour was blameless in the 2008 crash. By the same token, they are also never going to be persuaded that commentators like me were right to support the liberation of Iraq in 2003. As Alastair Campbell put it last week: “Although I can and will defend Tony over Iraq, I also know that we cannot overlook the fact that widespread opposition to the war, and anger about the aftermath, played a big part in Corbyn’s rise.”

True. Yet what remains of New Labour still risks becoming a restorationist sect. It wants to put the furniture back where it was in 2007. It wants to resume the show from the moment when it was so rudely interrupted. But that is a fool’s errand. If the Labour moderates wish to supplant Corbyn they must have the courage to start from scratch and to see New Labour for what it truly is: old.