COLUMBIA, S.C. - A South Carolina lobbyist resigned from a rival political campaign yesterday and then became the second man to claim that he had had a tryst with a Republican lawmaker trying to become the state's first female governor.

Lobbyist Larry Marchant admitted that he had no proof to back up his claim of a one-night stand with state Rep. Nikki Haley at a 2008 school-choice convention in Salt Lake City. Her campaign vehemently denied the allegation.

Earlier in the day, Marchant quit the campaign of Lt. Gov. Andre Bauer, who is running against Haley for the GOP nomination in the Tuesday primary.

"It never happened. Absolutely not," Haley said emphatically about Marchant's claim. "This is just disgusting politics. Two or three months ago I was Nikki who? and nobody was saying anything, and a couple weeks ago we started going double digits up in the polls, and now we have had everything thrown at us."

Last week, blogger Will Folks said that he and Haley, a tea-party favorite, had an "inappropriate physical relationship" in 2007.

Haley, 38, a mother of two, vows that she has been faithful over 13 years of marriage.