All about race. No its a question of:-

1) whether you keep going for the dumb alternative - Bush, Reagan fair enough - but....Sarah Palin!

2) America's mistrust of intellectuals.

3) the wisdom of fighting wars to install regimes that don't, on the face of it, seem very attractive.

4) the economy

Basically it all needs setting right, and McCain seems to offer the continuation of 'bad business as usuual'.