The Liberal Democrats face a choice of style and personality rather than of ideology. Forget about Nick Clegg being of the Centre Right or Chris Huhne the Centre Left. There is hardly anything between them in policy terms, as little as between, say, David and Ed Miliband, or Ed Balls and Yvette Cooper.

Mr Clegg and Mr Huhne are both free-market, green, libertarian, decentralisers, as well as being pro-European, although both as pragmatic realists, rather than in the unrepentant, integrationist style of, say, Andrew Duff, the leader of their MEPs.

Both wrote in the original free-market, pro-public service reform Orange Book of autumn 2004 but Mr Huhne has since distanced himself and played to the full his green credentials as environment spokesman. Mr Clegg has more sympathy with the “choice and diversity” agenda offered by David Laws on schools and Norman Lamb on health and he has faced the hard task as Home Affairs spokesman of sounding tough on crime and counter-terrorism, while being libertarian on immigration.

The two will seek to distance themselves during the campaign, but their common ground is large. The main alternative is likely to come from Steve Webb, with Susan Kramer possible as the fourth candidate.

Talk of a return by Charles Kennedy is absurd, because his candidacy would only damage him and his party.

Whoever stands, real policy differences are small. The party is committed to a shift in the tax burden away from income towards pollution, and to a redistributionist tilt to reduce poverty.

The Lib Dems’ problem is not a lack of policies. That gap has largely been filled under Sir Menzies Campbell’s leadership. His difficulty was, from the start, to face a squeeze from a rejuvenated Conservative Party under David Cameron and, then from this summer, from Labour after Gordon Brown took over. Any leader would have found it hard to be heard.

That is also why the new leader will face an uphill struggle of establishing a sufficiently distinctive position to be noticed. Mr Clegg and Mr Huhne are both bright and articulate, the former more comfortably so. Mr Clegg has easy charm in the Blair-Cameron mould, while Mr Huhne is more aggressive and suffers from being seen as arrogant. Nonetheless, while Mr Clegg is clearly the frontrunner at this stage, Mr Huhne showed 18 months ago that he can be both ruthless and effective. Mr Clegg’s main advantage is that he would be seen as fresh, youthful and interesting, attracting attention in ways that, unfairly, Sir Menzies never did. That, however, is only a quarter of the battle. The new leader, whoever he is (it will not be a she this time), will have to find a better and more coherent way of presenting the Lib Dems’ policies.

As all centre party leaders soon discover, they are usually price takers, rather than price makers. Most of the time they can only react to the opportunities left by the two main parties. These may exist as Mr Brown tries to reinvent himself and an already long-lived Labour Government as new, while Mr Cameron attempts to reconcile tax cutting and reform of public services. The prize will go to a leader who is energetic, telegenic, lively and, above all, resilient in unquestionably one of the most frustrating jobs in British politics.

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