While other Democratic ads have referred to Sanford's ethics violations and extramarital affair, a new one accuses him of shirking his gubernatorial duties during his five-day absense from the state in June 2009.
Sanford has acknowledged carrying on an extramarital affair with an Argentinian woman -- who is now his fiancee -- during the absence.
The new spot, sponsored by VoteVets, a Democratic 501(c)(4) that has ties to U.S. Senate Majority Leader Harry Reid, features retired National Guard Colonel Barry Wingard.
"If I had abandoned my post, I could be court-martialed," Wingard says in the ad. "It really hurt me, and I think it betrayed all of South Carolina and all of the citizens."
Several other national Democratic groups have launched anti-Sanford spots in recents days.
Sanford too has his own negative ad, attacking Democrat Elizabeth Colbert Busch that is airing now. Click here to watch that ad.
The VoteVets ad: