Equidistance is now the only policy that makes sense

For a politician whose experience was supposed to be his greatest asset, Sir Menzies Campbell displayed an extremely poor grasp of recent political history in allowing his party's spring conference to be overshadowed by speculation about who the Lib Dems would back in a hung Parliament and the suggestion that they would sustain a minority Labour government in power.

Before anyone tries to exonerate Ming by blaming the rogue briefing on some lowly press officer, I don't think that whether or not this was "authorised" is really the issue. It should have been made absolutely crystal clear that the whole subject was in fact completely off-limits, and this Ming and his chief-of-staff Ed Davey clearly failed to do.

Had Ming made a closer study of the 1987 election campaign in which he was originally elected to Parliament, he would have realised why. The Alliance campaign that year was wrecked by the fact that David Steel and David Owen each gave different answers to the question - Steel saying it was "inconceivable" he could do a deal with Mrs Thatcher - still alive it seems - and Owen maintaining he could never work with Neil Kinnock.

Similarly, in 1992, all Labour's talk of PR in the last week of the campaign strengthened the impression that a Lib Dem vote was a vote for Kinnock, swinging vital votes back to the Tories at the eleventh hour.

Maybe Campbell was trying to follow the example of his predecessor-but-one Paddy Ashdown, who formally abandoned "equidistance" after that election and came clean about the fact that he wanted a coalition with New Labour. At the time, it made good politics, enabling the Lib Dems to benefit from the wave of tactical anti-Tory voting that swept the country in 1997 and, to a slightly lesser extent, in 2001.

But thanks to the phenomenon of "tactical unwind," those days are behind us now. It follows that positioning the Lib Dems too closely to either of the two main parties is likely to prove counter-productive, especially in what is likely to be a very close race.

It is clear that in some respects, the Lib Dems remain to the left of Labour, notably on Iraq. It is also fairly obvious that Ming Campbell is more of an ideological bedfellow with Gordon Brown than with David Cameron.

But that means they need to work doubly hard not to give the impression that a vote for Campbell is a vote for Labour. I can't imagine this being a mistake that Chris Huhne would have made.