Nate Silver takes a stab at using his quantitative analysis skills to determine what can be learned about the effect of sex scandals in yesterday’s election of Mark Sanford to rep SC-1:
It would be wrong to conclude that voters did not punish Mr. Sanford at all for his extramarital affair. In fact, a reasonable number of voters did appear to hold it against him. Last November, Mitt Romney won South Carolina’s First District by 18 percentage points. Since Mr. Romney lost the election to Barack Obama by roughly four percentage points nationwide, that means the First District is about 22 percentage points more Republican than the country as a whole.
Mr. Sanford defeated his Democratic opponent, Elizabeth Colbert Busch, by nine percentage points instead – so one quick-and-dirty estimate is that Mr. Sanford’s personal history cost him a net of 13 percentage points. It just was not enough to flip the election result in such a conservative district.
As it happens, this 13-percentage-point penalty almost exactly matches an academic analysis on how much voters hold sex scandals against candidates. A 2011 paper by Nicholas Chad Long of St. Edward’s University, which examined United States senators running for re-election from 1974 to 2008, estimated that scandals involving immoral behavior lowered the share of the vote going to the incumbent by 6.5 percentage points.
Since reducing the incumbent’s vote share necessarily increases the challenger’s vote share, that means the net effect on the margin between the candidates is twice that amount, or 13 percentage points – just as we estimated it might have been for Mr. Sanford.
Silver cites other factors of unknown influence, including as Sanford’s experience edge, as a former Governor and congressman of the district, which encompasses Charleston, Myrtle Beach and most of South Carolina’s coast. Sanford’s nine point margin of victory is a disappointment, especially considering that Elizabeth Colbert Bush ran an aggressive campaign. She clearly understood that the sex scandal alone wasn’t enough to produce a victory. But perhaps she, or her supporters, could have hit a little harder on Sanford’s use of taxpayer dollars to conduct his affair.
Silver’s analysis seems reasonable enough. Most political observers are not all that surprised by Sanford’s win, since President Clinton’s popularity seemed to increase as a result of Ken Starr’s obsessive probe and Arnold Schwarzeneggar was elected governor of California amid multiple reports of marital infidelity. Still, it is interesting that sex scandals have so little impact — even in a state as archly-conservative as South Carolina.