The debate for Republican presidential candidates in Iowa last night lasted two hours, but it was a 35-second exchange that’s likely to be remembered.

The subject was Mitt Romney’s support for an individual health care mandate, and the nuances of his shifting positions. It led to this proposed wager, via TPM:

YouTube video

Rick Perry levied the initial charge, telling Romney, “I read your first book and it said in there that your mandate in Massachusetts which should be the model for the country. And I know it came out of the reprint of the book. But, you know, I’m just sayin’, you were for individual mandates, my friend.”

Romney responded, “You know what? You’ve raised that before, Rick. And– you’re simply wrong.” When Perry insisted the allegation is true, Romney replied, “Rick, I’ll tell you what. 10,000 bucks? $10,000 bet?”

Perry demurred, saying he’s not in “the bettin’ business,” but offered to show Romney a copy of his book.

On the substance, who’s right? Romney did make significant revisions to the second edition of his book, including language on health care policy, all of which appear to have been politically motivated. But while Romney supported a national health care mandate, it wasn’t explicitly part of his book. Perry was right on the larger point about the policy, but wrong about the source.

The larger problem, however, was the politics of a multi-millionaire vulture capitalist trying to intimidate a rival with his wealth. The vast majority of Americans don’t have $10,000 lying around to be used as a wager — it’s three months pay for most U.S. workers — and Romney’s off-the-cuff offer only reinforced the perception that he’s the out-of-touch elitist in the race.

The problem is compounded by the fact that it’s part of a pattern. Romney’s the guy who owns several mansions, one of which he’s quadrupling in size; he thinks it’s funny to joke about being unemployed; and in one striking instance, he didn’t have anything smaller than a $100 bill in his wallet while on the campaign trail.

Adding insult to injury, in the same debate in which Romney offered to make a $10,000 bet, he also dismissed a middle-class payroll tax break as an insignificant “band aid.”

The next time Romney presents himself as being in the middle class, despite his $250 million, voters might be inclined to just laugh in his face.

Eric Fehrnstrom, a senior Romney adviser, seemed to think this wasn’t a damaging moment at all for the former governor. I doubt even he believes this line. The other Republican candidates are already pouncing on this; Democrats can hardly believe their good fortune; and the media appears to have latched onto this as the key development of the night. If this was the night Romney planned to stop Newt Gingrich’s momentum and get back on track, it was a failure.

One more thought on this: watching the clip, it looked to me like this was Romney just saying what was on his mind. In other words, for all of Romney’s overly-slick, robotic presentation, I doubt this was a scripted talking point or a prepared response. It was just the candidate being the candidate.

It’s why “just be yourself” probably isn’t good advice for Mitt Romney.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.