We may well have reached “peak Momentum”. These are the most favourable political circumstances Labour’s hard left could envisage. They feel politically vindicated by the general election result, have a well-funded, well-staffed organisation holding a vast amount of data on Labour members and have reshaped Labour’s membership through successive rounds of mass recruitment.

And yet the centre-left still, annoyingly for Momentum, lives on and fights on, securing a reasonable tally of NEC nominations, fending off most of the attempts to deselect councillors – except in the hot spot of Haringey – and even winning some of the early parliamentary selections.

There are limits to the support Momentum can attract within the party and in the wider electorate.

First, the clock is ticking in terms of the age of the key players on the Labour left. Jeremy Corbyn is 68. Whilst he appears to be in good shape and revitalised by the general election campaign, and would undoubtedly fight another early election, if the parliament goes the whole five years he may not want to take office as PM aged 73.

John McDonnell will be 70 by then. Diane Abbott will be 68. The younger generation of left MPs doesn’t include anyone who looks ready to become leader yet. The obvious contenders to succeed Jeremy should he retire – who are very publicly on the campaign trail already – are from the soft left not the hard left. It is the space in the party around where Ed Miliband was and to the left of that, but not aligned with Momentum and the Bennite or Corbynite tradition.

Momentum’s traction with the unions is also limited with only one of the four largest unions supporting them.

Among the party membership, only 31,000 are Momentum members and 100,000 on the Momentum email list. The remainder of those members who voted for Corbyn to be leader in 2015 and 2016 are not necessarily aligned with the far left and seem open-minded in local selections. There is a core constituency for the centre-left of 44-72,000 people who voted against Momentum in the 2016 NEC elections, 50,000-55,000 who voted against Momentum in the 2017 CAC elections, and 116,000 members, 36,000 registered supporters and 39,000 affiliated supporters who voted for Owen Smith in the 2016 leadership contest. Even where these people have dropped out of party membership they can be re-recruited in the right circumstances.

In the wider electorate, the strategy of mobilising and increasing turnout among a radical base succeeded in increasing Labour’s vote dramatically in 2017 but, except in Scotland, it is not clear that there are any more left votes like this to squeeze out.

In England, they are in the wrong places anyway. Labour has already won almost every inner city seat and university town. Piling up super-majorities there does not help gain seats in a first-past-the-post election system. There is no way round the task of winning working class and lower middle class voters direct from Tories in traditional marginal towns and suburbs, the kind of people who voted Labour in 1997, 2001 and 2005 but not since then. It is difficult to see how a pitch to them can be developed that doesn’t involve ditching some of what makes Jeremy Corbyn fundamentally Jeremy Corbyn.

Opinion polls – whilst immeasurably better than before the general election – show us stuck in a dead heat with the Tories despite their shambolic performance, not making the kind of breakthrough into leads sufficient to deliver a Commons majority. The detail of the polls shows we have not answered the fundamental concerns the electorate had about Labour in 2015 about the strength of our leadership and our economic competence. We may however, have answered the question mark voters had about Ed Miliband’s perceived weakness on immigration, as Corbyn has moved to his right on this issue by opposing EU freedom of movement.

If we do win an election then that will have partly been achieved with centre-left votes while centre-left Labour MPs will be the holding balance of power in the Commons. Even the most bloodcurdling calls for de-selection aren’t going to create a PLP of 326 Momentum supporters. These MPs will have a moral duty to use their votes in the Commons to veto anything that would damage national security, the same way that Corbyn felt he had a moral duty to vote against the Iraq War, though I am clear that they should fully support our government’s domestic programme as any differences there will be ones of technical policy rather than high moral principle.

The biggest problem Labour’s centre-left faces is to regain our intellectual and political self confidence after an election that disproved our long-held and evidence-based assumption about the electability of the hard left.

Our ideas are better than Momentum’s as they are based on the realities of governance not on theorising and sloganising.

Our wing of the party is the only one with a proven track record of winning elections, governing and tackling poverty and inequality. As of now, Momentum just have slogans.

Social democracy is a more attractive ideology than far left socialism and its authoritarian variants, which is why Momentum is trying to steal our clothes, for instance writers who support them are self-describing with the odd amalgam “Class War social democrats”.

But, if Momentum is just social democratic “Old Labour”, why did Benn and Corbyn and McDonnell attack Wilson and Callaghan so much in the 1970s? Why do people associated with Momentum reject aspects of Attlee’s legacy like Nato? Why do they look for overseas models in authoritarian Venezuela and Cuba not social democratic Sweden and Denmark?

Our behaviour is also something we should take pride in. It’s not Labour’s centre-left bullying online or in meeting. It’s not us threatening to deselect our opponents. It’s not us who fail to tackle antisemitism. It’s not us who praise dictatorships. It’s not us who support foreign and defence policies that would put our country in peril.

There is more raw talent and brains on our side of the party, much of it languishing on the backbenches in parliament or quietly getting on with running local councils and creating and defending social justice in local communities.

Our views are nearer those of the electorate. Every opinion poll on political beliefs shows British public opinion is a bell curve with most voters near the middle. The most recent such poll from Opinium showed only 10 per cent of voters see themselves as left-wing, 15 per cent as centre-left, 45 per cent centrist, 17 per cent centre-right and 13 per cent right-wing.

So we are in the absurd situation where Momentum, whose politics is only shared by 10 per cent of the population, is the tail wagging the dog of a 40 per cent party that needs to be a 45 per cent party to win.

This is both the answer to how Labour wins and how we win within the party. The other 75 per cent of Labour voters need to take back control of their party and make it able to reach the next slice of voters necessary for a Labour parliamentary majority.

We have to build up our capacity to out-recruit Momentum by mobilising the larger latent public support of the centre-left and some centrists who want an electable Labour Party. This will require huge investment in digital and press recruitment advertising, coherent messaging, an attractive candidate for whenever Jeremy retires, and fresh policies, not 1997 answers to 2017 problems (though these are preferable to 1917 or 1977 ones).

We need to appeal to young people as well as Middle England – Blair did in 1997 – they are not fundamentally attracted to the hard-left, they are just angry about student debt, housing costs and graduate unemployment and low wages.

In the mean time there is no point trying to re-open the question of Corbyn’s leadership – that is settled until he wants to retire or loses another election. But there is every point trying to stop Momentum from getting further influence and to drive them back at every level of the party structure. The next leader needs to inherit as much sensible architecture of the party as possible, otherwise they will end up spending energy that should be spent on beating the Tories on restoring the party to common sense.

There should be no organisational equivalent of Danegeld to the Vikings – trying to cut deals and surrender territory to Momentum to save our own skin. They will see this as weakness, the only language they understand is being out-voted.

Sadly, the existence of Momentum requires similar factional rigidity and structure on our side – organised local moderate groups with a broad enough appeal to be a political home for any member not in Momentum, systematic mobilisation to attend key party meetings and vote in internal ballots, safe spaces to develop political education and confidence and solidarity.

This is contrary to the historic culture of the Labour Party, which until 2015 was not factional, but failure to build our own structures means inevitable defeat if Momentum is disciplined and organised and we are buzzing around them as an incoherent rabble of individualists.

Centre-left MPs need to demonstrate public leadership not by critiquing Corbyn but positively by developing new policies, showcasing their own talents so it is obvious the wrong people are on backbenches, and out organising Momentum in their own CLPs.

Over time we need to peel of the good people in Momentum, the idealistic John Lennonists, from the Lenininsts. This requires a friendly, open and inclusive approach at a local level. The experience of the 1980s was that Bennites who got involved in campaigning moved to the centre as they got fed up with losing and heard what working class voters actually thought, and that those who became councillors had their politics reshaped by the realities of taking decisions in power.

We need to rebuild the 1985-1997 alliance of the soft left and centre-left. This may even mean the party being led by someone from the soft left, but backed by the centre-left, as in the Kinnock era.

More than anything, the centre-left needs to stop seeing Momentum as invincible – recent selections show it is not – and needs to try to enjoy the process of out-arguing and out-organising them. We are winning where people are organising and standing up for themselves, and losing mainly where people’s spirit has been broken and after initial defeat they have quit the party or stopped turning up to meetings.

We need happy warriors. We are living in the worst-case scenario for people with our politics – but there is nothing more they can take from us, because we have nothing to lose. In decades to come we will want to be able to look young members in the eye when they ask “what did you do to save the Labour Party from Momentum?”

The scale of the task whilst huge is actually minuscule compared with the situation that confronted the people now running Momentum and the party as recently as May 2015. If they can do it, we can do it.