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SALT LAKE CITY — When the presidential candidates headed to South Carolina last week, political pundits bubbled with anticipation, looking to see who would launch the lowest blow on a field infamous for fierce, no holds-barred battles. Surely few would have predicted that the biggest punch would come from ABC, which aired a voyeuristic and hostile interview with one of Newt Gingrich's ex-wives. The candidates themselves have been comparatively mild.

South Carolina may not be the birthplace of guerrilla warfare, but it certainly was its nursery. During the Revolutionary War, Francis Marion earned the nickname the "Swamp Fox" here by engineering hit and run tactics against the British, hitting them where they weren't and disappearing into the brush. Today, South Carolina is known for guerilla electoral tactics. But is this reputation fair? The answer is yes and no. No, South Carolina probably does not suffer from a more poisonous a political culture than other states. Yes, the presidential primary season there is rough, mainly because of the state's role as the third strike for failing candidacies and the quick pace of the race after a leisurely New Hampshire contest.

The state has had its share of iconic negative moments. In 2000, anonymous phone calls planted the racially-charged lie that John McCain had fathered an illegitimate black child. In 2007, an anonymous mailing purported to be a Christmas card from Mitt Romney, complete with controversial quotes from 19th century Mormon leaders. A Romney staffer then created PhonyFred.org, a website trashing Fred Thompson, which was traced to a server at the Romney camp. The staffer was fired and the website disowned. This tradition of dirty politics in South Carolina reaches back to Lee Atwater in 1980, who planted false news stories that played on racial fears of white voters. All of these were anonymous whisper campaigns, the classic "dirty trick."

But are South Carolina politics uniquely underhanded? To find out, we ran a rough content analysis to see which states were mentioned online in connection with "push polling" and "anonymous mailers," two standby dirty tricks techniques. Controlling for population, South Carolina actually did surprisingly well, ranking sixth cleanest among the states.

If South Carolina's political culture is unremarkable, why are its primaries so mean? The answer, says Peter Wielhouwer of Western Michigan University, who studies campaign ethics, "is desperation and the pace of the race." Desperate candidates may have one last chance in South Carolina, he says, and only two weeks to work it from the time the New Hampshire primary ends. "The speed shifts after ten months shaking hands in Iowa and New Hampshire."

That requires radio and television ads, and air time means negative advertising, the most effective tool for highlighting differences and halting an opponent's momentum. Wielhouwer draws a distinction between negative and dirty campaigns, noting research that shows that negative ads are actually much more informative than positive.

The measure of negative ads, he says, hinges on their accuracy and relevance, for which the voter might look for a consensus among various fact checkers. For example, the anti-Romney film run by Gingrich supporters in South Carolina got a four "Pinocchios" from the fact checkers at the Washington Post.