(CNN) - The two Republicans vying for a spot on the ballot in South Carolina's special U.S. Congressional election traded barbs Thursday over former Gov. Mark Sanford's history of marital infidelity.
Opponent Curtis Bostic claimed the former governor was a "compromised candidate" because of an extramarital affair with a woman in Argentina in 2009 during his tenure in the state house.
"Trust is a crucial issue. In fact, it has become a crucial issue in this race," Bostic said during Thursday's debate. A former Charleston city councilman, Bostic will face Sanford in a runoff vote on Tuesday because neither candidate received a majority in last week's primary.
The seat up for grabs is South Carolina's 1st Congressional District, which Sanford represented from 1995 to 2001. He went on to become the Palmetto State's governor, during which time his affair became public.
He and his wife divorced in 2010, and Sanford completed his second term in 2011. He's now engaged to the woman with whom he had the affair.
During his primary campaign, Sanford told CNN he was seeking "redemption" by running for office again, a sentiment he returned to Thursday.
"The events of 2009 absolutely represent a failure on my part, for which there were and probably always will be consequences," Sanford said. "But that does not mean, because you have had failure in your personal life, that you cannot step back into life again."
Bostic, however, argued that the congressional seat - which has been held by a Republican since 1981 - would become vulnerable if Sanford becomes the GOP nominee.
"A compromised candidate is not what we need. It's just not what we need. We need to secure this seat. It needs to be red," Bostic said, citing polls showing that Democratic candidate Elizabeth Colbert Busch is leading Sanford.
Sanford asserted it was too early to consult polls because voters haven't yet had a chance to fully assess Colbert Busch's record.
And as for the charge that he's a "compromised candidate" based on his affair, Sanford said that every human had faults and that at least his were in the open.
"My faults are out - exposed - and all I can say, I have learned mightily from all of those mistakes," Sanford said, adding later that "both of us have vulnerabilities that (Colbert Busch) would try to exploit."