Ezra Klein and Jason Zengerle agree that "Fred Thompson is to the Republicans in '08 as Wes Clark was to the Democrats in '04. In other words, the highpoint of his campaign will be the day he gets in the race, because once he's a serious candidate--and not just the fevered daydream of a dissatisfied base--voters will realize he's not all that."
I agree that Thompson's luster is likely to fade. But what happened with Clark is that it seemed like he'd be a strong candidate -- military background, southerner, etc. -- but then it turned out he was really bad at campaigning. Thompson's actually campaigned before and it seems he was pretty good at it. If he stumbles, it'll be for some other, not-especially-Clark-like reasons.