As a Republican running in what promises to be a tough political climate, there's a strong case that he ought to pick someone the press will cast as a "moderate" choice, rather than a partisan one. (Florida Governor Charlie Crist is an possible fit in this category, and of course there's always McCain's great friend Joe Lieberman.) But as the maverick nominee of a party whose rank-and-file regard him with some suspicion, there's also a case that McCain needs to make a pick that shores up his base, whether it's someone like Mitt Romney, still the darling of the right-wing intelligentsia, or a lesser-known right-winger like South Carolina Governor Mark Sanford.
The obvious way to thread this needle would be for McCain to find a reformist right-winger -- a politician who passes most conservative litmus tests but has shown a heterodox streak and a zest for policy innovation as well, and who's far enough from Washington to be untainted by the scandals and debacles associated with the Bush-era GOP.
"If you have a problem, go meditate or go on a vacation. Don't think about it."