(CNN) – Mark Sanford overcame the latest hurdle in his South Carolina political redemption tour, ending Tuesday night with a concession from his opponent in the GOP primary runoff for a U.S. House seat.
Results showed the former South Carolina governor had 57% of the vote, compared with 43% held by former Charleston City Councilman Curtis Bostic. That was a difference of about 6,000 votes out of about 45,000 cast.
Jake Tapper interviews Mark Sanford Wednesday on "The Lead" - 4 p.m. ET, only on CNN.
Sanford said he was “humbled” and “thankful” for the win, calling his competitor “a gentleman.”
His fiancee, Maria Belen Chapur, made a rare public appearance, standing at his side Tuesday evening. Revelations about his extramarital affair with her in 2009 led many observers to conclude his political career was over.
“I congratulate the governor on his race,” Bostic told supporters after conceding. “I want to be the first to say, ‘Congratulations, campaign well-run, we wish you the very, very best.’ ”
Sanford now goes on to the May 7 special election against Democratic nominee Elizabeth Colbert Busch.
In a statement Tuesday night, she said she looked forward to a “vigorous campaign” and said the heavily Republican district needs “a voice in Washington who stands up for South Carolina solutions – not either political party.”
National Republican Congressional Committee Chairman Greg Walden wrote in a statement that “South Carolina families clearly deserve a continuation of the strong fiscal discipline displayed by now-Senator Tim Scott and will greatly benefit from Sanford’s fiscal hawk approach. Without a doubt, Mark Sanford will campaign tirelessly to grow South Carolina jobs and work to get our nation’s massive spending problem under control.”
Sanford's past infidelity is front and center in battle for the state's 1st Congressional District, which he represented from 1995 to 2001 before being elected the Palmetto State's governor for two terms.
In his victory speech Tuesday night, Sanford thanked voters, saying that while God forgives, “sometimes the voters aren’t so forgiving.”
Bostic claimed in Thursday's debate that Sanford was a "compromised candidate" because of his extramarital affair with a woman from Argentina. The affair came to light in 2009, sinking any hopes Sanford had of making a bid for the GOP presidential nomination in 2012.
"Trust is a crucial issue,” he said. “In fact, it has become a crucial issue in this race."
Sanford and his then-wife, Jenny, were divorced in 2010, and Sanford finished his second term as governor in January 2011. He's now engaged to the woman with whom he had the affair.
Sanford, who's touting his fiscal conservative credentials as he campaigns for Congress, is 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 finished with 37% of the vote, far short of the 50% needed to avoid a runoff. But he was far ahead of Bostic, who narrowly edged out state Sen. Larry Grooms to finish second with 13%.
Sanford said his first-place finish was "incredibly humbling."
"The events of 2009 absolutely represent a failure on my part, for which there were and probably always will be consequences," added Sanford. "But that does not mean, because you have had failure in your personal life, that you cannot step back into life again."
But Bostic, who had won the support of some top social conservative leaders, disagreed, arguing that the congressional seat - which has been held by the GOP since 1981 - would become vulnerable if Sanford became the Republican 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 surveys that indicated that Colbert Busch was leading Sanford.
But Bostic did not repeat his criticism of Sanford's infidelity at their second debate last weekend.
Colbert Busch is the sister of Stephen Colbert, the satirist and host of "The Colbert Report" on Comedy Central. He's campaigned on his sister's behalf, recently telling Jake Tapper, CNN’s chief Washington correspondent and anchor of CNN's The Lead, that "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 Busch, an official with Clemson University's wind turbine drive testing facility, is expected to have an uphill climb in the general election because the district is heavily Republican.
GOP 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 of South Carolina 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 his seat.
– CNN’s Steve Brusk and Gregory Wallace contributed to this report