(CNN) -- Mark Sanford is another step closer to political redemption, but the real headline out of his Tuesday victory in a Republican primary runoff for his old congressional seat was a rare public appearance by his former mistress -- who's now his fiancée.
And while the former South Carolina governor is considered the favorite in next month's general election showdown with Democratic nominee Elizabeth Colbert Busch, the sister of satirist and Comedy Central host Stephen Colbert, his past infidelity remains front and center in the race and could continue to hurt him with crucial female voters.
Democrats wasted no time in attacking Sanford over the affair.
"This is the same Mark Sanford who, as governor, disappeared from office and used taxpayer money to visit his mistress. With all the issues we are working on, we do not need him in Congress," wrote Sen. Kirsten Gillibrand of New York in a fundraising e-mail for Colbert Busch sent in the hours after Sanford's victory. "Fortunately, there is a strong independent woman running to give us a better alternative named Elizabeth Colbert Busch."
Sanford addressed his "incredibly long journey" at his victory celebration over former Charleston County Councilman Curtis Bostic. "In that journey, I am humbled." He added that while God forgives, "sometimes the voters aren't so forgiving."
Sanford thanked supporters, family, and his fiancée, Maria Belen Chapur of Argentina. The former governor said Wednesday on CNN's "The Lead with Jake Tapper" that he was surprised by her appearance at the victory celebration.
"She completely surprised me," Sanford told CNN Chief Washington Correspondent Jake Tapper. "It was an awfully, awfully nice surprise."
"I didn't know she was coming, but I'm excited to see her," he said.
The affair came to light in 2009, after Sanford disappeared from public view for several days and re-emerged, claiming he'd been hiking the Appalachian Trail. He later admitted that he was actually in Argentina, seeing his lover. The episode sank any hopes Sanford had of making a bid for the 2012 GOP presidential nomination. Sanford and then-wife Jenny were divorced in 2010 and he finished his second term as governor in January 2011, exiting to what many thought would be political obscurity.
Sanford is touting his fiscal conservative credentials as he campaigns for Congress, but he's also asking the public for a second chance, telling CNN that he was seeking "redemption" by running for office again.
He came in first in a 16-candidate primary two weeks ago, but only with 37% of the vote, far short of the 50% needed to avoid a runoff. He topped Bostic in Tuesday's runoff by a 57%-43% margin.
Bostic appeared to try to make infidelity a key issue in the runoff campaign. "Trust is a crucial issue. In fact, it has become a crucial issue in this race," the candidate said at a debate with Sanford last week. Bostic added that the former governor was a "compromised candidate" because of the affair.
Now Sanford faces off May 7 with Colbert Busch, an official with Clemson University's wind turbine drive testing facility. She is expected to have an uphill climb in the general election because the district is heavily Republican. The 1st District has been in GOP hands for more than three decades.
Rep. Tim Scott won re-election to the seat by 27 percentage points in last November's election. But when Republican U.S. Sen. Jim DeMint stepped down from his seat late last year to take over as the head of the conservative Heritage Foundation, GOP Gov. Nikki Haley named Scott to fill the seat, triggering the special election to fill the seat that Sanford held for three terms before becoming governor.
Mark Sanford: Shamed politician fights for comeback
Colbert Busch's famous brother has campaigned on his sister's behalf.
"She's my sister, and I'm willing to, you know, break the jewel of my own creation to try to do something for her," Colbert told Jake Tapper, CNN's chief Washington correspondent and anchor of CNN's "The Lead."
Colbert will team up again with his sister for fundraisers later this month in the nation's capital and in New York.
But Democrats are focusing on Sanford's affair.
"The families of this district need a representative who they can trust," Colbert Busch campaign spokesman James Smith said Tuesday night. "Mark Sanford simply has the wrong values for our community.
Democratic Congressional Campaign Committee press secretary Emily Bittner tried to put Rep. Cathy McMorris Rodgers, a senior House Republican, on the spot.
"Even Republicans acknowledge that Congressman Sanford's behavior was a disgrace and that he betrayed the public trust, so will Congresswoman McMorris Rodgers support Mark Sanford in his quest to return to Washington?"
Sanford disagrees, saying his runoff victory shows he doesn't have a problem with female voters, at least those in his party.
There were a lot of Republican conservative women that voted last night. And what they did was decided to send me in as the Republican standard-bearer in this congressional seat," Sanford told Tapper.
But some South Carolina Republicans disagree, saying that the female vote could be an issue for Sanford.
"Surveys show Sanford has a problem with women, and some may never forgive him," said Republican strategist Bruce Haynes, a partner in the consulting firm Purple Strategies. "Acknowledgment of perceptions is the first step in rebuilding any reputation, and his choice to bring his fianceé forward is smart."
"His past and his present relationship with her is an unavoidable issue in this race. It's best that he acknowledge it, deal with it on his terms rather than let others define it for him. Otherwise, silence is hiding, and hiding is guilt, and guilt is losing," added Haynes, who served as chief of staff for former Republican Rep. Bob Inglis of South Carolina, and as a staff member for former GOP Gov. Carroll Campbell.
Haynes thinks Sanford can win a race that focuses on policy, but says a race on personality will be much harder to win.
Republican strategist Hogan Gidley, who served as executive director of the South Carolina Republican Party, agreed.
"It's going to be virtually impossible for Mark Sanford to attack Colbert Busch," said Gidley, who worked for Sanford rival state Sen. Larry Grooms in the primary. "It's extremely tricky political territory for several reasons: One, Sanford can't effectively execute an apology tour and consistently be on the attack; two, any political attack on Colbert Busch would be used against Sanford and the party as proof of a perceived 'war on women;' three, we have a huge problem right now with the women vote -- so any candidate perceived to be one who disregards women -- is going to face issues getting votes."
But the geography of the district may be in Sanford's favor.
"The new 1st District is a coastal area, so it's generally the most socially liberal of South Carolina's GOP-held districts," Haynes said. "This is because coastal communities are historically more diverse and concerned about issues like the environment that carry less importance inland."