If, as we believe, a brand is a promise, then the recent general election should in theory have seen branding at its best. It didn’t really happen though, did it? Despite claims and counter-claims about the results, no one won. And it looks as though a long term casualty may be the Liberal Democrats.

It all looked different a couple of weeks ago. ‘I agree with’ Nick had burst upon a surprised and charmed ITV1 audience. If he had said to his supporters, as David Steel famously did, ‘Go back to your constituencies and prepare for government’, they would have agreed with him.

If the Liberal Democrats wanted only to be kingmakers, they have got that wish. But it’s difficult to imagine anyone in the polling station deciding to vote for the kingmaker rather than the king. Indeed, it can be argued that support for the LibDems fell away just as Nick was talking about doing deals with anyone other than Gordon Brown.

There are, of course, political reasons why the LibDems failed to make a breakthrough. But from a branding perspective, the party has both suffered and benefited from being the third party in a duopoly.

Suffering comes from being squeezed: it’s difficult to be distinctly different when you’re seen to be in the middle of a standard left-right continuum. And as both Labour and the Conservatives have moved back to embrace the centre, it’s all to easy for the public to assume that when policy is being debated, the LibDems split the difference between the other parties. Other than on the economy, where Vince Cable caught media attention not for – as he kindly so often reminds us – predicting the financial meltdown but for his soundbite about Gordon Brown at Prime Minister’s Questions – ‘The House has noticed the Prime Minister’s remarkable transformation in the past few weeks from Stalin to Mr. Bean’, that isn’t going to change. The right wing media will trash the LibDem immigration policy, and the media on the left will be excited about potential electoral change, but neither will in the end define the LibDem brand.

It could perhaps have been different. Nick Clegg played the ‘new politics’ card for all he was worth. But I suspect that with the economy where it is, complex ideas about voting systems lack immediacy. The Tory plans to cut the number of MPs, while fundamentally flawed (and guaranteed to raise the cost of politics) seemed simple enough. In the end, the only LibDem policy that people really seemed to know about and warm to was their proposals for income tax.

The LibDems benefited, of course, from not being one of the others. So in 2005, Labour supporters could vote for the LibDems in protest at the Iraq war without having to vote Tory. Equally, as the Conservative brand became contaminated in the 1990s, the LibDems were able to attract former Tories.

All that changes as a result of last Thursday. If Clegg and his party prop up the Conservatives, then those of their supporters who loathe the Tories will simply not forgive them. Their home as an anti-Tory vote for those disaffected by Labour will be destroyed. Half their promise – that they are a safe anti-Labour vote – will have been broken. That leaves being a safe anti-Tory vote.

Of course, should Clegg and co. prop up Labour, then these arguments apply, but in reverse.

The politics may force Nick Clegg to do a deal. But he shouldn’t forget that politicians are about promises. Beware the damage to the Liberal Democrat brand.