One error Romney made is that a wager on his part would have been politically more palatable than a bet. The subject matter in question is Romney's own words; he is presumably quite aware of what he said. Therefore, he's proposing what appears to be a sucker bet, which would create a $10K debt for Perry, which seems unfair. Also, gambling is offensive to some voters; Perry's refusal to go there scored points for him at Romney's expense.

Even a wager (where payment would occur only if Perry could prove his case) would carry the risk of Romney being perceived as something of a crackpot, or someone who reneges on a wager, if Perry could make a convincing case.