It seems pretty clear that the last two contenders for the Conservative Party leadership will be David Davis and David Cameron. The media are speculating that the momentum is all with Cameron and that Clarke's supporters will all switch to him. They might be surprised.
People switch from one candidate to another for all sorts of reasons and see all sorts of talents in the contenders. You cannot simply place the candidates on a two dimensional spectrum and jump to conclusions. The argument goes that Clarke's supporters are on the left and so will shift to the moderniser. In actuality, not all Clarke's supporters are on the left: some of them like him because of his experience, or his aggressive style. In anycase, the media assumption that 'modern' is the opposite of 'right wing' betrays more about the media mindset than about the realities of politics.
Davis's support could crumble, and Fox could be in the final round against Cameron, but the likelihood is that Davis will pick up a surprising number of votes from Clarke.
So, Davis or Cameron? Both have merits, but Cameron's rumoured commitment to abandon the policy of education vouchers counts very strongly against him. You cannot increase opportunities while only the rich - who can afford to pay for public services twice - have choice in health or education.