Following Vince Cable’s announcement that he will step down as party leader in May it is now do or die for the Lib Dems.

Since the electoral disaster of 2015, the party has struggled to make its voice heard. On Brexit, it has taken a principled stance in support of a second referendum. Yet while that policy appeals to many liberally minded people, it has had little impact in the opinion polls. The party has hovered consistently at around 10 per cent when people are asked about voting intentions.

Cable himself, a clever man, is liked by the party faithful – but he does not inspire. Then again, in almost any other circumstances he would never have become leader.

Such was the scale of Lib Dem defeat four years ago that Cable himself appeared to have been consigned to parliamentary history – booted out by the constituents of Twickenham on a night when the size of the party’s Commons contingent fell from 57 to eight.

However, Theresa May’s fateful decision to call a snap election in 2017, allied to Tim Farron’s largely inept leadership in the interim, gave Cable a second chance. Jo Swinson’s decision not to run against him for the top job meant Vince was a shoo-in.

Which MPs defected to form Change UK? Show all 12 1 /12 Which MPs defected to form Change UK? Which MPs defected to form Change UK? Change UK Details on the individual MPs are in the following photos Reuters Which MPs defected to form Change UK? Heidi Allen Anti-Brexit MP for South Cambridgeshire resigned from the Conservative party on February 20 PA Which MPs defected to form Change UK? Chuka Umunna MP for Streatham since 2010 and prominent People's Vote supporter PA Which MPs defected to form Change UK? Anna Soubry The prominent anti-Brexit MP for Broxtowe resigned from the Conservative party on February 20 PA Which MPs defected to form Change UK? Luciana Berger MP for Liverpool Wavertree since 2010, resigned from the Labour Party over bullying and anti-semitism PA Which MPs defected to form Change UK? Sarah Wollaston Anti-Brexit MP for Totnes resigned from the Conservative party on February 20 PA Which MPs defected to form Change UK? Joan Ryan MP for Enfield North resigned from the Labour party on February 19 citing its tolerance of a "culture of anti-Jewish racism" PA Which MPs defected to form Change UK? Ann Coffey MP for Stockport since 1992 Chris McAndrew / UK Parliament Which MPs defected to form Change UK? Gavin Shuker MP for Luton South since 2010 Getty Which MPs defected to form Change UK? Chris Leslie MP for Nottingham East since 2010 PA Which MPs defected to form Change UK? Mike Gapes MP for Ilford South since 1992 PA Which MPs defected to form Change UK? Angela Smith MP for Penistone and Stocksbridge since 2010

Still, he has proved unable to revitalise the Liberal Democrats and is right to depart sooner rather than later – especially with no end to the Brexit fandango in sight.

The question of who should replace him is important of course. Swinson is the obvious choice, but Layla Moran could run her close and may be the sparkier candidate. Ed Davey, capable politician though he is, has probably missed his chance.

But the party needs to do more than simply pick a new leader, it must develop a new vision – or at the very least communicate a version of the existing one that feels coherent, holistic and relevant.

At a time when both the main parties have drifted further left and right, it has felt odd that the Lib Dems, grounded a little to the left of centre, have been unable to offer a cogent alternative.

The experience of coalition government should have given the party confidence. Instead it left a rump; battered and bruised – and convinced of few things aside from the idea that it must move away from the Nick Clegg era. All understandable in the immediate term, but a mistake nonetheless. In any event, Cable – a minister in that coalition government – would never have been able to achieve such distance and instead found himself caught between two stools.

What complicates matters further in 2019 is the emergence of the Independent Group, the collective of ex-Labour and ex-Tory MPs who have not only put up their stall somewhere in the political centre ground (exactly where remains unclear), but who have promised a new way of doing politics. A third of those questioned in a recent poll said they would consider voting for an Independent Group candidate.

Have they spiked Lib Dem guns then? Perhaps, although with TIG still not yet a party and without firm policy or election plans, there is room for Swinson or Moran (or whoever else) to step up and offer a more plausible “third way”: empowering individuals; reclaiming the green territory, an equal focus on community and the advantages of globalisation; nurturing creativity.

That said, as and when a general election comes along, the Lib Dems will need to think long and hard about whether to make an accommodation with TIG.

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Members would, for the most part, baulk at any talk of merger (despite or because of the party’s own history) – but an electoral pact would make sense, at least insofar as agreeing that Lib Dem candidates should not run against the existing TIG MPs. And if the Independent Group puts up additional candidates, the agreement should work in the other direction too.