If he didn't seek reelection then that might be a sign. If he were to run again and lose, that might hurt his chances.
It wouldn't just hurt his chances. He'd be finished. It's hard to get taken seriously as a presidential candidate when you've lost your most recent statewide election. Which is why, if he really wants to run for president in 2012, he shouldn't bother risking another race for governor. Instead, he should pull a Mitt Romney, and spend the last two years of his term as governor taking actions designed to set himself up as a top tier presidential contender (of course, this shouldn't require as much flip-flopping as in the case of Romney).
How about General Petraeus, wouldn't he be considered a top-tier Presidential candidate also?
