Anthony Wells has a typically encyclopaedic post up regarding Ken Clarke's entry to the Tory leadership campaign. There's all the usual Wellsian statsy goodness, and some very interesting points about just how popular the lover of, ahem, smoky late night jazz is, despite being unfashionable on Europe and, as AW points out, frequently despised when he was in power.
Wells argues that, although he would draw in voters who would otherwise not vote Conservative in spades, the problem is whether or not he would alienate as big a chunk of the Tory core vote. That's obviously a problem, but I wonder how big a one it really is. After all, there are a hell of a lot more people in the sets "wouldn't otherwise vote Tory but might if Clarke was leader" and "will vote Tory even if Osama bin Laden was leader and pledged to nationalise sex" than there are in the set "Clarke is a Eurolizard come to curdle my precious bodily fluids". Brutally, there aren't enough true believer Tories for him to frighten away enough of them to outweigh the possible gains. And they are getting less common all the time.
If the Tories reject Clarke, or a Clarke-equivalent like Malcolm Rifkind, again, they are following a strategy that goes entirely against the logic of the British constitution. In our first-past-the-post system, coalitions happen inside parties rather than inside parliament. It's all about getting together 51% by broadening your base. Bizarrely, the party most hostile to proportional representation is behaving - unconsciously no doubt - exactly as if it was living under PR by trimming its strategy to its radicals rather than the other way round. Strange, innit?