Which Tory leader-candidate is the more Eurosceptic? It's hard to say. Both are playing to the Eurosceptic gallery, but I get the impression that although neither want to be held hostage to unworkable pledges, both have allowed themselves to be bounced further than they would have liked by some of their supporters on the lunatic fringe.

David Davis was John Major’s whip when the Maastricht Treaty was approved by the House of Commons, and is therefore mistrusted by the Eurosceptics. He was later Minister for Europe during the start of the negotiations on the Amsterdam Treaty. I saw him close up at this stage, because I attended those talks as an advisor to Elisabeth Guigou, the European Parliament representative.

At that point he was trying to be all things to all people. He is now persevering with that tactic, pledging to hold not just one, but two referenda on opting out of (rather than trying to change) some European policies (selected by him) that we have, up to now, agreed with our neighbours.

As the Independent put it in their leader (subscription required):

“His proposal to hold two referendums on 'bringing back power' from Europe is also unrealistic. Has he considered the implications of tearing up treaties with our continental neighbours? It is a Eurosceptic fantasy to imagine that this can be easily done. The trouble with virtually all of Mr Davis's policy ideas is that they give the impression of having been formulated in a previous era."

Davis has, however, not yet pledged to take the Tories out of the main centre-right grouping in the European Parliament where they now sit with the likes of the German Christian Democrats, the Swedish and Danish Conservatives, Mr Berlusconi’s Forza Italia, the French Gaullists and so on. Perhaps he realises that such a course would leave their MEPs totally marginalised and without influence in the European Parliament.

But Mr Cameron has proposed precisely that, to the consternation of the majority of Tory MEPs. Perhaps for this reason, combined with their mistrust of Davis, he has received the support of the most extreme and obsessed Tory eurosceptics such as David Heathcoat-Amory, Bill Cash, Daniel Hannan and the maverick Roger Helmer.

But I have another suspicion. Maybe Cameron has calculated that such a promise is eye-catchingly attractive to the eurosceptics, but would in fact never need to be delivered upon, as the MEPs would veto it? Perhaps he's less eurosceptic than he wants his supporters to believe. After all, he's apparently chosen Edward Llewellyn, a fellow Old Etonian and relatively sensible Europhile who once worked for Chris Patten, as his chief of staff. And he also let slip to the Telegraph’s Comment column that he feels "we should be proud of the fact that we are a leading member of the European Union".

Who knows? But one thing seems certain: the Conservatives will continue to pull themselves apart over Europe!