There’s one thing Jeremy Corbyn could do that would make him the next Prime Minister

In rejecting a progressive alliance, the Labour leader might be missing an opportunity to give his new politics the booster rockets it needs

Labour leader Jeremy Corbyn has dismissed the idea of leaving the Richmond Park by-election uncontested to give the Liberal Democrats a chance to remove Zac Goldsmith (PA)

At last year’s general election, progressive parties won 49 per cent of the vote between them, and the Conservatives and Ukip totalled 51 per cent. Sound familiar? Yes, eerily close to the 52/48 per cent vote to leave the EU. We are a nation split down the middle.

But although Labour, the Liberal Democrats, the Greens and nationalist parties in Scotland and Wales command the support of half the country, they seem a million miles from winning power nationally. Whenever Theresa May calls an election, she will be well placed to extend her slender majority. If she waits until 2020, new parliamentary boundaries will give the Tories a 20-seat advantage. A long spell of one-party rule looks very likely.

This bleak landscape for progressives has sparked a lively debate in Labour’s ranks about whether it should support proportional representation and seek a progressive alliance with centre-left parties in the hope of maximising the anti-Tory vote.

It’s not a new debate, and usually breaks out when Labour’s prospects are poor. The Tribalist Tendency, who are wedded to the current first-past-the-post system, point out that the progressive prophets of doom made similar predictions before Labour won three big majorities under Tony Blair. But this time Labour’s discussion might just lead somewhere. Many of the Labour members attracted by Jeremy Corbyn are fluid in their politics – former Greens, for example – and more open to co-operation with other parties.

A fringe meeting on PR at last month’s Labour conference attracted 300 people – up from just 15 last year. Some trade unions, pessimistic about Labour’s chances of winning an overall majority, now back PR, as do a new generation of pluralist Labour MPs including Chuka Umunna and Stephen Kinnock.

This week three of them urged Labour not to field a candidate in the 1 December by-election in Richmond Park triggered by Zac Goldsmith’s resignation over the proposed third runway at Heathrow. Labour frontbenchers Clive Lewis and Jonathan Reynolds and former Shadow Cabinet member Lisa Nandy said Labour should give the Liberal Democrats a free run in a seat they held until 2010, which would significantly boost their chances of defeating Goldsmith, who is standing as an independent but will not be opposed by the Tories. The Lib Dems are making it a “Brexit by-election” as well as opposing Heathrow expansion. Ukip’s decision to back Goldsmith is a decidedly mixed blessing and may help the Lib Dems woo the 72 per cent of voters in the constituency who backed Remain.

You might think that the new politics Corbyn champions would embrace electoral reform and a progressive alliance; John McDonnell, his closest ally and the Shadow Chancellor, supports PR. But although aides insist Corbyn has an open mind, Labour’s decision to field a candidate in Richmond suggests otherwise. Corbyn is said to be unhappy about the three MPs’ call for Labour to stand aside.

Of course, a leader aspiring to govern the country does not want to look weak. If Labour talked up co-operation with other parties that would be seized on by the media as evidence that it could not win under its own steam. The Conservatives would love to re-run the 2015 election, when the prospect of a post-election deal with the SNP damaged Labour, and warn voters against electing a “coalition of losers.”

Yet Corbyn might be missing an opportunity to give his new politics the booster rockets it needs. Perhaps he doesn’t want to do it when Brexit is so high on the agenda, in which case Labour will leave the field clear for the Lib Dems to become “the party of the 48 per cent”.

Yet slowly, Labour’s tectonic plates are starting to shift. Labour’s policy-making annual conference could vote on electoral reform before the next election. Privately, Labour figures reach out to other parties. Lewis, who like Nandy is a possible future Labour leader, has a good working relationship with Caroline Lucas, co-leader of the Green Party. She has floated the idea of “progressive primaries” to choose a single candidate in some seats.

A small number of local anti-Tory pacts might be sought at the next election. On current form, Labour might stamp on the idea. That would be a mistake. For Labour to come round, it might take a crushing electoral defeat and a longer spell in the wilderness.

There is still time for a rethink. Neal Lawson, a former Gordon Brown aide who chairs the Labour pressure group Compass, has been banging on about a progressive alliance for years but now sees signs that the tide is turning. He warns that even if Corbyn achieves his goal of boosting Labour’s membership to one million people, he would not be able to command such an army in the Facebook generation in which people shop around.

As Lawson put it: “Labour will become plural and transform itself, or it will grip onto the 20th century and die and a new vehicle of this century will be created to replace it.”