Sanford had 54 percent of the vote to 45 percent for Colbert Busch, with 70 percent of the precincts counted in the 1st Congressional District race, CNN reported.
Sanford won the special election to replace Tim Scott, who Gov. Nikki Haley named to fill the U.S. Senate seat vacated by Jim DeMint this year, USA Today reported. DeMint resigned to lead the Heritage Foundation think tank.
The victory solidifies Sanford's campaign to overcome the revelation of his 2009 affair that clouded his final years as governor, ended his marriage and derailed national political aspirations. During the campaign, ads criticized Sanford for leaving the country while governor to visit his Argentine lover, who now is his fiancee.
Colbert Bush, sister of Comedy Central political satirist Stephen Colbert, lost in her bid to win a seat that has gone to Republicans for the past 30 years.
Sanford will appear in Charleston County Family Court Thursday to face a trespassing complaint from his ex-wife, Jenny Sanford.