“Get some fat men around him!” That was the message that Damian McBride, Gordon Brown’s disgraced former spin doctor, sent to one of Ed Miliband’s aides immediately after Miliband won the Labour leadership contest in 2010. By “fat men”, he meant fixers, arm-breakers: those who knew how the Labour Party worked from the inside and could bend it to the new leader’s will.

It never quite happened. “We were tired, our friends on other campaigns had gone on holiday, we’d just won [a leadership] election – but actually that was when we lost [the general election of 2015],” one veteran of the Miliband camp told me. Ed Miliband never lost the reputation that he acquired early on as a well-meaning but odd fellow who had “stabbed his brother in the back”.

One consequence of Labour’s long leadership election, now as in 2010, is that Jeremy Corbyn’s closest aides – those he has grown to trust over many years in parliament and throughout the campaign – are exhausted and error-prone, just as the public begins to take its first proper look at the new leader. Corbyn’s likeable and well-regarded press chief, Carmel Nolan, has reached the end of her contract and may not make the transition to the leader’s office. Labour headquarters has been raided of talent, first by rival leadership campaigns and also by Sadiq Khan for his tilt at the London mayoralty next May.

Fatigue lay behind Corbyn’s decision to give the airwaves the miss in the days after his victory on 12 September, leaving the field clear for his opponents to traduce him. Rather than speak to broadcasters, Corbyn instead embarked on a chaotic reshuffle on 13 September.

First impressions haven’t been good but, unlike Ed Miliband, Corbyn does at least have the services of a fat man, the ultimate “fixer’s fixer” in the words of an admirer: Tom Watson, the new deputy leader of the party. Watson, who knows Labour ­better than most, was one of Gordon Brown’s chief enforcers. On 7 September he set out a series of red lines on policy that put him in direct opposition to Corbyn: unequivocal if not unromantic support for an “In” vote in the coming referendum on Britain’s membership of the European Union and continued British membership of Nato. Watson is implacably opposed, too, to plans to bring back the mandatory reselection of MPs, a move favoured by some of Corbyn’s closest allies. And yet, Watson has fallen in line behind the veteran left-winger.

He did so because it wasn’t just that New Labour died on 12 September, although it certainly did in spectacular fashion – Yvette Cooper, Gordon Brown’s last true heir, finished third, while Liz Kendall, the Blairite candidate, came a distant fourth with just 4.5 per cent of the vote. It was more that the Corbyn victory also marked the demise of Labour’s “soft left”. It was the soft left that, in 1981, broke from Labour’s “hard left” and voted for Denis Healey over Tony Benn in their battle for the deputy leadership. It was the soft left that, under Neil Kinnock’s leadership, expelled the Militant faction from the party in 1986 and ditched much of the disastrous 1983 manifesto. It was also the soft left that voted for Tony Blair in 1994.

After the flirtation with a leftward shift under Ed Miliband, supporters of Cooper, Kendall and Andy Burnham all expected the soft left to return to its old habits and elect a moderate leader. Instead, for the first time in three decades, Labour’s soft left voted with its heart, not its head, and by a margin so large that no Labour MP can contemplate moving against Corbyn, at least not in the near term.

Now, in place of the soft left, a new group, with Watson pre-eminent, is being born: the “soft right”. These are politicians who are far more moderate than Corbyn but who believe, in the words of one: “We’re going to have to try to make this work.” Two politicians have already emerged as major players: Michael Dugher, Burnham’s campaign chief, and Jon Ashworth, a key supporter of

Yvette Cooper. On 13 September, they began calling opposition frontbenchers, putting the case to them for staying in post under Corbyn. For the most part, they were unsuccessful: Corbyn’s shadow cabinet is significantly further to the left than Miliband’s, with most of the centrists out in the cold.

Yet there are still representatives from the party’s moderate wing. Burnham is shadow home secretary, after all, while his allies Charles Falconer, Hilary Benn and Lucy Powell have been given plum positions shadowing Justice, Foreign Affairs and Education.

It is the politicians with superficially less high-powered roles, however, who hold real power and on whom much of the future prospects of Labour’s moderates now rest: Rosie Winterton, who remains as shadow chief whip, Dugher, Ashworth and Gloria De Piero. De Piero, like Dugher and Ashworth, is a protégée of Watson. Winterton, though officially neutral during the leadership contest, was Watson’s nominee for the post of chief whip five years ago.

Ashworth sits on the party’s ruling ­National Executive Committee, notionally as one of the leader’s picks but in reality as a voice for stability and unity, rather than one advocating fundamental change to the party’s structures. And Dugher, the new shadow culture secretary, will be insulated in his role from some of Corbyn’s more

radical positions.

And De Piero? She has the newly created post of “shadow minister for young people and voter registration”, with the right to attend shadow cabinet. The brief gives her licence to travel the country, meeting members, winning them over – ready, perhaps, for the moment when Watson, in his guise as shadow secretary of state for the sword of Damocles, moves against Corbyn.

Stephen Bush is the editor of the Staggers, the New Statesman’s politics blog