The oddest thing about Romney's $10k bet in last night's debate is that it didn't seem to be a gaffe, made on the spur of the moment. It seems to have been pre-meditated. Somebody must have told him, this is a really good idea, Mitt. That person, presuming they're still on staff, must be feeling pretty stupid today.
I'm not actually convinced it was as devastating a moment for Romney as some are suggesting, but it's become the main talking point of the post-debate analyses, and that's not good for him. Not because it reminds voters that he is rich - they know that, and generally aren't resentful of wealthy politicians - but for two other reasons.
First, it means people are talking about a negative moment for Romney in a debate, for the first time, (while Newt came through unscathed). The air of invulnerability he carried with him into each debate has been dispelled.
Second, and more fundamentally, it has turned a cruel spotlight on Romney's biggest weakness: his reputation as a flip-flopper. That's why Huntsman's ad, above, is so effective (and see Perry's here). The mistake wasn't so much the size of the bet as the fact that by attempting to create a 'moment', the Romney camp have only ended up drawing attention to their candidate's fatal flaw.
(Useful round-up of debate reactions here.)