The face-off between David Cameron and David Davis this afternoon on Jonathan Dimbleby’s show leaves me feeling very nervous about the Conservative Party’s fortunes. If David Cameron does win the leadership contest - as is being widely predicted - then we have an uncertain future. On today’s performance Mr Cameron seems to have a fair bit to do before he can be considered a self-assured performer of Davis’ calibre.

After the usual setting out of stalls in which David Cameron talked again about how ‘we have to face up to the big challenges that the country faces’ and the need ‘to change the party’ - phrases so Blairesque in their total absence of meaning that I am aghast his advisors let him say them any more - he warmed up with a sensible sounding piece about how we should support the government when it gets things right because to do otherwise constitutes ‘opportunistic opposition’.

This was in reference particularly to the government’s education white paper - described by Shirley Williams and a Times journalist on ‘Question Time’ this week as so full of contradictions that it rendered itself meaningless - and which David Cameron himself had said illustrated that the government was too timid in its education changes.

David Davis pointed out to Mr Cameron that you need to be careful how you support this bill because if you’ve already called it ‘timid’ - which Mr Cameron has - and the government is already backtracking on the paper anyway - which it is - you could easily find you’ve actually supported a bill that provides a worse outcome than you expected. You end up being an accomplice to a bad bill.

David Cameron ignored this piece of advice and simply restated that it was principled to support the government when it did right.

In fact, Mr Cameron made quite a bit about how conservatives should ’stick to their principles’ and be ‘consistent’. That’s music to my ears actually and something I believe we have failed miserably to do for years. Indeed, when asked by an audience member whether he could convince people he wouldn’t be taken apart by Blair and Brown Mr Cameron replied, “They will take apart someone who doesn’t stick to their principles. We do get taken apart when we’re opportunistic.”

Mr Davis, who had listened to Mr Cameron’s various pronouncements on consistency and principle pounced: “You talk about consistency, David, but before the election you supported our policy on immigration, on tuition fees, on healthcare… you’ve changed your mind on the back of a single election loss. That’s not consistent. That can easily be represented - maybe misrepresented - as opportunistic on the back of one election result.”

Cameron: “If we don’t make changes we will lose again.”

So badly caught out was Mr Cameron I genuinely felt bad for him. There was worse for him to come.

Jonathan Dimbleby on Cameron’s opposition to patients’ passports: “… a classic example of what would open you up to the charge of opportunism. You fought passionately in favour of patient passports before the election and now you’re junking them.”

Mr Cameron’s answer revealed much. The policy was wrong, he said, “because it gave people the impression it was helping people escape the NHS.”

So the policy was wrong not because it was actually wrong in itself but because of the image it portrayed? So might Mr Cameron actually believe it was a good policy that simply looked bad? This little episode emphasised one of the more crucial differences between the two contenders: if it’s right Davis will argue it out - even if it’s controversial. Cameron may well junk it.

Mr Dimbleby to David Cameron: “Were you aware [before the election] this policy [patients’ passports] favoured the middle classes or didn’t you recognise it?”

Despite Mr Cameron’s attempts to sidestep the question Mr Dimbleby was dogged in trying to get an answer leading Mr Cameron to resort to a tactic similar to the one he used in the first Question Time head to head - attack the questioner. “You’re interrupting me more than Paxman,” he accused.

The audience laughed but for those of us who wonder if we’re looking at our Party’s future leader this was not funny.

The drugs issue is Mr Cameron’s achilles heel - and not just because of his own possible use in the past. It doesn’t help that his inconsistency when calling for consistency is so see-through:

“I want a drugs policy that works and not just one that sounds good.” Yet he dropped patients’ passports when they didn’t sound good.

Leaving aside David Cameron’s ham-fisted approach to the drugs issue - he seemed to believe that the sending of the correct ‘message’ to youngsters about drugs depended on whether you categorised drugs sensibly - the real problem is that, in a relatively friendly, relatively calm debating arena he loses out on fundamental points and ends up looking amateur. If Dimbleby - the presenter - and Davis can rattle him in what is only a hint at what will come if he’s elected leader then what will Labour’s big guns do to him?

Once again I find myself looking at the older man as being the one best placed to land the blows on Labour and best placed to make sensible, level-headed decisions with regards to his own Party. He seems the one least likely to be caught out saying one thing while doing (or having done) another. Davis is a safe pair of hands with the necessary experience and maturity to guide the Conservative Party through opposition and into power. Cameron is a great Conservative MP. I don’t think he’s yet a leader.