Every general election presents the Liberal Democrats with a challenge. How should they position themselves against Labour and the Conservatives? Over the years they have tried a variety of tactics. A glance back at them helps us to understand the way Jo Swinson is wrestling with that question today.

In February 1974, the Liberals argued that they were Britain’s only radical party. They asked of their two rivals: “Which twin is the Tory?” Their vote more than doubled to 19 per cent, but they won only 14 seats.

In 1983, the Liberal/Social Democratic Party Alliance sought to “break the mould” of British politics by replacing Labour as Britain’s main progressive party. They came close in votes (Labour 28 per cent, Alliance 26 per cent), but Labour still won almost ten times as many seats (209 versus 23).

In terms of seats gained, the Lib Dems’ most successful election by far was 1997. They jumped from 20 MPs to 46—the largest third-party number since 1929. Actually, the party’s vote share slipped slightly, from 18 to 17 per cent; but tactical voting by Labour supporters helped Lib Dem candidates defeat more than two dozen incumbent Tories. It helped that Paddy Ashdown, the Lib Dem leader, abandoned the party’s policy of equidistance between Labour and the Conservatives, and moved closer to Tony Blair and New Labour.

There is one obvious example of the Lib Dems co-operating with the Tories—after the 2010 election. Nick Clegg’s party paid the price: it lost 49 of its 57 seats.

Today, Swinson finds it far easier to say what she doesn’t want than what she does. She hates Boris Johnson’s Brexit, and Jeremy Corbyn’s far left prospectus. She says she wants to be prime minister; but she knows that this is nonsense. Corbyn is more likely to become Chief Rabbi.

More relevantly, she says that if we end up with another hung parliament, she won’t prop up either Johnson or Corbyn. This leads to the obvious follow-up point: since one of them is almost certain to be prime minister after the election, she really should tell her voters what she would do.

Here is my suggestion. It is not to change her stance but to make it more credible.

Swinson’s starting point…

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