Former South Carolina Gov. Mark Sanford, who left office in 2011 after an extramarital affair with an Argentinean woman, won the Republican nomination for the May 7 special election to fill a U.S. House seat he held for three terms. 

He beat Republican rival Curtis Bostic with about 57 percent of the vote.

"It's been a very long journey. And in that journey I am humbled to find ourselves where we find ourselves tonight," said Sanford Tuesday night in his victory speech. 

His now fiancee, María Belen Chapur, appeared at Sanford's side during his victory speech, smiling and applauding. It was her first public appearance with Sanford, and the former governor thanked her for being long-suffering while he was campaigning. She did not address the crowd.

Sanford will face Democrat Elizabeth Colbert Busch, the sister of comedian Stephen Colbert, and Green Party candidate Eugene Platt in a May special election.

Four years ago as governor, Sanford was mentioned as a potential GOP presidential candidate. But he vanished from the state for five days and reporters were told he was hiking the Appalachian Trail.

He later returned and tearfully acknowledged at a Statehouse news conference he had been in Argentina visiting Chapur, with whom he was having an extramarital affair. Sanford's wife Jenny later divorced him.

Sanford said he was surprised Chapur, who still lives in Argentina, attended the press conference.

"She's going to show up when she wants to show up," Sanford said when asked if she would be campaigning. "She's going to be a part of what she wants to be part of and if she doesn't want to be part of it, she won't. She's a very private person."

Sanford has said the couple plans to marry this year.

"Their plans as a couple are personal and we'll keep them personal," campaign spokesman Joel Sawyer said when asked if a date has been set. He said for now, Sanford is focused on the campaign.

Before leaving office as governor, Sanford avoided impeachment but was censured by the Legislature over state travel expenses he used for the affair. He also had to pay more than $70,000 in ethics fines — still the largest in state history — after Associated Press investigations raised questions about his use of state, private and commercial aircraft.

Based on reporting by The Associated Press.

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