If MPs from Labour and the Lib Dems want to form a new party, the time to do it is now

Sir Vince Cable has confirmed Westminster’s worst-kept secret: now 75, he will not lead his Liberal Democrat party into the general election due in 2022. The party will choose his successor “once Brexit is resolved or stopped,” he announced.

So, with even Theresa May’s allies admitting she will not take the Conservatives into another election, Jeremy Corbyn will likely be the last of the three current main party leaders still standing in 2022.

How different will politics look by then? Very, if Cable gets his way. In a speech in London on Friday, the Lib Dem leader set out plans to turn his party into a much wider “movement for moderates” before standing down, probably next year.

Cable’s ideas are sound: allowing liberal-minded voters to sign up as supporters for free and vote in leadership elections, and allowing a non-MP to run for leader. “It’s ludicrous to restrict the choice of leader to 12 people,” one of the 12 Lib Dem MPs admitted.

Cable’s speech was a compliment to Momentum, Corbyn’s grassroots fan club. But therein lies the Lib Dems’ problem: Corbyn has hoovered up the insurgent vote, which the Lib Dems lost when they hopped into bed with the Tories in 2010. And, despite sitting on the fence on Brexit, Corbyn has managed to scoop up most of the Remain vote too.

The blunt truth is that principled opposition to Brexit, and calling for a Final Say referendum, has not revived the Lib Dems in the way Cable hoped when he became leader after last year’s election. The 48 per cent became only 8 per cent in the opinion polls. “We are still tarnished by the coalition,” one senior Lib Dem told me. “We need to be rebranded. We might need to be part of something else.”

Cable was candid in his speech: liberal democracy in Britain is “in grave danger”, perhaps the gravest since the 1930s. So his party needs to “remake itself in the public mind”.

The former business secretary hopes his legacy will be a party strong enough to provide the platform for a new centre force, able to fill a vacuum left by two main parties who have moved to the extremes. He hopes some anti-Corbyn Labour MPs will break away from their party, and some Tories will walk out if Boris Johnson or another hardline Eurosceptic succeeds May.

While Cable naturally argued that any defectors should join his ready-made centre party, the real question is whether the Lib Dems would merge with a new party. That would be opposed by some Lib Dem traditionalists, happier to guard the party’s democratic rulebook than become the “mass movement” Cable wants.

He hinted that the Lib Dems should throw in their lot with any new party rather than compete with it. “We have to engage in party realignment,” he said. “This requires us to demand better than the usual tribalism – of ourselves and of our partners... We hang together or we hang separately.”

Cable is right: the Lib Dems have nowhere else to go. “Vince is fishing for partners, looking for something, anything,” said a Labour figure who might be one architect of a new party. As I reported last month, a Labour split looks increasingly likely. After the antisemitism row, there is now another factor. The no confidence motions in the MPs Joan Ryan and Gavin Shuker passed by their constituency parties on Thursday night will be seen as a prelude to deselection. Corbyn is unlikely to intervene to save such MPs; those ousted in this way may feel they have nothing to lose by forming a new party.

That prospect moved a step closer on Friday when Tony Blair told the BBC that voters would not “tolerate” a choice between Corbyn and (Boris) Johnson at the next election. “Something will fill that vacuum,” he said. Blair conceded it might not be possible for centrists to regain control of Labour – a recognition that dreams among Corbyn critics of recruiting “an army of moderates” lie in tatters. It was a hint Blair does not agree with those who intend to stay and fight inside Labour in the hope that the Corbyn tide eventually goes out.

A split among the Tories is less likely; their hunger for power makes them more loyal to their tribe and many MPs are determined to block Boris.

Although we might have a New Lab-Lib party by the 2022 election, it will be very difficult to break through under our archaic first-past-the-post system. Not least because it is not easy to see who would be its Emmanuel Macron or Justin Trudeau figure. The SDP had big names when it broke from Labour in 1981 and still failed to break the mould (just). To have any chance, a new third force should not be about Brexit or rejoining the EU, and would need a strong, distinctive domestic agenda so it can answer the vital questions: what, and who, is it for?