Who would be a successful Republican candidate in 2012. I take this to mean “someone who could plausibly defeat President Obama’s bid for re-election.”
My somewhat uninformed guesses: David Petraeus and Colin Powell (who’d have all kinds of difficulty winning the primary). These accomplished generals share one related trait: deep credibility as men who are serious about national security, enabling them to run as sane, experienced stewards, rather than bellicose idiots so desperate to seem toughest on terrorism that they spend the primaries calling for “doubling Gitmo” and competing to see who would torture in more contrived ticking time bomb situations.
They’re also both post-partisan figures of the kind that Americans seem to like, haven’t got long voting records to be picked apart, and can nevertheless credibly claim more executive experience than President Obama.
I’m sure there are other candidates who could also mount a credible challenge, though I don’t know who they are. Folks who can’t unseat President Obama, in my quite fallible opinion: Mitt Romney, who might actually make a good president, Sarah Palin, who wouldn’t, Ron Paul, who the American people would never elect, and Mike Huckabee, who would spend lots of money at home and abroad.