A Truly Special Election in South Carolina

Former South Carolina Gov. Mark Sanford addresses supporters in Charleston, S.C., on Tuesday, March 19, 2013, after advancing to the GOP primary runoff in a race for a vacant South Carolina congressional seat. (National Journal)

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If only for entertainment, the most compelling contest this year is South Carolina's special election, which could pit former Gov. Mark Sanford against the sister of comedian Stephen Colbert. If Sanford wins a runoff Tuesday against conservative activist Curtis Bostic — hardly a foregone conclusion — he would face Elizabeth Colbert-Busch on May 7.

Conventional wisdom suggests Sanford would start as a front-runner in a Republican district that gave Mitt Romney 58 percent of the vote. But scandal-plagued candidates are uniquely vulnerable, even in the most favorable districts. Even though he may win a runoff against an underfunded Republican, Sanford's approval ratings are weak and he remains vulnerable against a credible Democrat.

It's an open question whether Colbert-Busch fits that bill. One Democratic automated poll showed the race deadlocked, but privately Democrats are taking a wait-and-see approach. And Democratic strategists are keeping a close eye on the contest, knowing that an upset in South Carolina could perpetuate the narrative of ongoing GOP woes.