By Harriet McLeod
CHARLESTON, S.C., April 2 (Reuters) - Voters in South Carolina's coastal first congressional district will choose on Tuesday between former Governor Mark Sanford and former Charleston County Council member Curtis Bostic as the Republican nominee for the open seat.
Sanford gained national notoriety as the state's governor in 2009 when he left South Carolina for six days, telling aides he was hiking the Appalachian Trail when he was in fact visiting his mistress in Argentina.
Despite that history, the 52-year-old candidate was the top Republican in an earlier round of voting and held the lead in a recent poll.
His challenger, 49-year-old Bostic, has at times tried to make Sanford's lapse an issue in the race, calling his rival "a compromised candidate" during a debate in Charleston on Thursday.
Sanford had the support of 53 percent of likely voters in the Republican primary, to 40 percent who supported Bostic, in a tally released last week by Public Policy Polling.
Both men have touted their fiscal conservatism and said they oppose same-sex marriage.
After the news of Sanford's affair broke, his wife divorced him, he paid more than $70,000 in ethics fines and he was censured by the legislature, though he served out the remainder of his term as governor. He is now engaged to the woman, Argentine journalist Maria Belen Chapur.
Sanford chided Bostic, an attorney and former Marine, for missing a number of meetings when he served on the Charleston County Council. Bostic said his wife had undergone treatment for cancer and that he missed meetings to take care of her.
Sanford's campaign touted that the National Review had called him "the taxpayers' choice," while Bostic said he was supported by former 1st District Congressman Henry Brown.
Republican Senator Tim Scott, who vacated the seat when he was appointed to the U.S. Senate, has not endorsed a candidate.
Governor Nikki Haley appointed Scott to the Senate in December to replace Jim DeMint, who resigned from office to head the Heritage Foundation, a conservative think tank.
Only voters who participated in the first-round primary two weeks ago can vote in the run-off, said Gibbs Knotts, a political scientist at the College of Charleston.
"I suspect that turnout will be low and that many of the supporters of the 14 unsuccessful Republican candidates will stay home," he said.
The winner of the run-off will challenge Democrat Elizabeth Colbert Busch, the sister of TV comedian and political satirist Stephen Colbert, in the Republican-leaning district's special election on May 7. (Editing by Colleen Jenkins and Eric Walsh)
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