The Lib Dem manifesto has put too many eggs in the Brexit basket

The problem is that the 48 per cent have splintered. The British way, it seems, is to move on, and get on with Brexit

Liberal Democrats leader Tim Farron greets supporters during a General Election campaign visit to Portsmouth (PA)

It seemed a good idea when the Brexit vote happened. The Liberal Democrats were flatlining on 8 per cent in the opinion polls, one per cent for each of their MPs. So the 48 per cent who backed Remain looked heaven-sent.

Tim Farron’s enthusiasm had to be tempered a little by some senior colleagues. His initial pledge to fight the next general election on a promise to take Britain back into the EU was diluted to offering a referendum on the exit deal, with Remain on the ballot paper.

When Farron proudly crowned himself “Remoaner of the Year”, some colleagues doubted it would help the Lib Dems regain their South West heartland, ruthlessly captured by their Tory Coalition “partners” in 2010. The doubters were proved right at this month’s local elections, when the party went backwards. It now averages nine per cent in the opinion polls.

The problem is that the 48 per cent have splintered. The British way, it seems, is to move on, and get on with Brexit. This is good news for Theresa May, and one reason why she called an election before the economic downside of Brexit hits home. It is bad news for the Lib Dems. According to YouGov, the Prime Minister is fishing for votes in a big pool – 68 per cent of the electorate, composed of 45 per cent of Hard Leavers who backed Brexit in the referendum plus 23 per cent, the Re-Leavers who voted Remain but think the Government has a duty to quit the EU.

With Ukip on life support, the Tories are scooping up six in 10 of this group. Meanwhile, the Lib Dems, Labour and the Greens compete in a much smaller pool – Hard Remainers, the 22 per cent of the electorate who want the referendum result overturned. Our outdated first-past-the-post system exaggerates this Brexit effect, loading the dice in the Tories’ favour.

Perhaps the Lib Dems have put too many eggs in the Brexit basket. Their manifesto, published today, tries a bit too hard to make the connection. They rightly put a heavy emphasis on children and young adults, but argued in a statement: “Nothing is more important to our children’s future than Brexit. A bad Brexit deal, with Britain outside the single market, will wreck the future for our children, our economy and our schools and hospitals."

There are plenty of good ideas in the manifesto. The Lib Dems propose a 1p rise on all income tax rates to raise £6bn a year, ring-fenced for the NHS, social care and public health.

The Tories, who stole the Lib Dems’ flagship policy of raising the personal tax allowance in the Coalition and got all the credit, should repeat the trick on health. Norman Lamb, the Lib Dem health spokesman, is leading an all-party effort to persuade May to override long-standing Treasury objections to an earmarked tax rise. Number 10’s door was not entirely shut in his face.

The Lib Dems are right to pledge another £7bn for schools. They also outbid Labour, which got in a pickle over welfare, by pledging to spend £9.7bn on reversing Tory benefit cuts.

But this is a fantasy figure. Even Farron admits his party has no chance of winning power. He has ruled out joining a coalition with May or Jeremy Corbyn – not that there is any chance of one after this one-sided contest. He must be the first party leader in history who wants to become Leader of the Opposition, the most difficult job in British politics. But his goal of overtaking Labour will not be realised at this election.

That doesn’t mean a vote for the Lib Dems is a wasted one, especially if you oppose Brexit or a hard Brexit. They did their duty by forming the Coalition in 2010. They may have another one to perform after this election. It is increasingly clear that Corbyn intends to carry on even if Labour suffers a crushing defeat – or at least ensure that the left keeps it grip on the reins of power.

Although Yvette Cooper and Chuka Umunna would be among those ready to challenge Corbyn in a leadership contest, Labour centrists are far from optimistic about regaining control. Some start to think the previously unthinkable – walking out on Labour to form a new, pro-European centre party, probably with the Lib Dems and possibly with some refugees from the Cameron-Osborne tribe exiled by May.

Senior Lib Dems are thinking along similar lines. Farron can’t easily say it as he leads his troops into battle. But Nick Clegg, Paddy Ashdown and Sir Vince Cable have all put a toe in the water by raising the prospect of a new centre force, which might be the only way to end one-party rule.

The Lib Dems might not look very important at this election. But they could become very important after it.