Former South Carolina governor Mark Sanford (R) addressed his dramatic 2009 fall from grace at a debate Thursday night, saying he failed in a very public way but emerged with humility that would serve him well in Congress.

"My faults are out and they are exposed," Sanford said. "But all I can say is that I have learned mightily from every one of those mistakes."

After disappearing from the state for nearly a week as governor in 2009, Sanford revealed an extramarital affair, a stunning admission for the onetime rising GOP star. He served out the remainder of his term and is now trying to win back the 1st district congressional seat he once held.

Declaring that he "failed very publicly," Sanford argued that he's been humbled by his missteps. The ability to confront one's flaws, he offered, is an important trait. "I think that what it brings is a level of humility that frankly is desperately needed in Washington, D.C.," said Sanford.

Without ever directly addressing Sanford's affair or his disappearance, his opponent, Curtis Bostic (R), said that if the former governor wins the GOP nomination, he will be a weak candidate against Democratic nominee Elizabeth Colbert Busch, because of trust issues.

"Trust is not had. ... A compromised candidate is not what we need," Bostic said.

Sanford rebutted: "While my skeletons are certainly out there, they're out there." He slammed Bostic for missing meetings on the Charleston County Council and failing to make a campaign finance disclosure.

Bostic then appeared to take a veiled swipe at Sanford, responding that he missed meetings because he was taking care of his wife, who was fighting cancer.

"My absence is because I was home taking care of her largely, doing what I should have been," said Bostic. "People knew where I was, I did my job just the same."

With just days to make up ground against a better-known and better-funded candidate, Bostic is trying to rally the support of conservatives. Former presidential candidate Rick Santorum stumped Wednesday for the underdog, who has a strong base of Christian conservative supporters.

Sanford finished well ahead of the pack in last week's GOP primary, but failed to win a majority of the vote, triggering a runoff next Tuesday. Bostic barely edged into the runoff after a recount confirmed his narrow advantage over third-place finisher Larry Grooms.

The debate between Sanford and Bostic began in cordial fashion. The two even joked about pausing for the designated time to interrupt one another. Later, it grew more contentious.

Time and again, Bostic, a former Marine, pitched himself as a constitutional conservative, pointed to his ability to cultivate relationships, and noted his military background.

"I'm asking for a new, fresh opportunity. Somebody with new ideas; a fresh face, a relationship builder," he said.

He jabbed at Sanford's record in Congress, noting that none of Sanford's bills or resolutions were passed in the House.

Both candidates portrayed themselves as strong fiscal conservatives dedicated to reining in federal spending. Sanford argued that his tenure in Congress during the late 1990s afforded him relationships with members who are now in positions of power.

"I think that it would matter that some of the folks that I got to know when I was there almost 20, 15 years ago are now in leadership positions within the House."