Don't know. I actually think a good part of avoiding this is not allowing it to become too personal....that you're so riled up by the other guy's negative ads that you think you have to keep firing back, even while the whole back-and-forth is becoming mutually destructive. Starkest example of this I've ever seen was the 1992 WI Dem. Senate primary (I lived in WI at the time, and was only in high school, but I was just starting to get interested in politics) between Russ Feingold, Joe Checota, and Jim Moody, in which Checota and Moody were the early frontrunners, and they just destroyed each other with negative ads, and kept going after each other even after Feingold started to pull ahead because the feud had taken on a life of its own. Feingold ultimately destroyed them in the primary despite have the least amount of $ of the three, because the other two had spent all their $ attacking each other. (OK, maybe this is starting to drift off topic, but the point is that Clinton and Obama should avoid that if they're smart.
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