John O’Sullivan suggests Obama-Webb versus McCain-Romney. Obviously, I tend to find the first more plausible then the second though I suppose you could argue that Webb’s appeal to working-class whites is more theoretical than Romney’s appeal to anti-McCain conservatives. At least some of them. But there is no way Mitt Romney can put Massachusetts in play, especially not in light of recent events.
For my money, the Onion has most accurately captured the 2008 presidential race: a nightmare ticket of Obama, Clinton, and McCain.