Just as state Rep. Nikki Haley (R)[pictured] was beginning to gain momentum in South Carolina’s competitive four-way June 8 gubernatorial primary — especially after winning Sarah Palin’s endorsement — this story has the potential to dramatically alter the race to succeed Gov. Mark Sanford (R).

Will Folks, a prominent South Carolina Republican blogger who was Sanford’s former press secretary, admits to having an “inappropriate physical relationship” with Haley “several years ago.” Haley has been married to her husband, Michael, for 13 years, and they have two children.

Folks suggests that he’s revealing his past relationship with Haley because it’s being leaked to news organizations.

“It is what it is, and aside from the Haley family – Michael, Nikki, Rena and Nalin – I feel no need to apologize or explain myself to anyone. People are human. We make mistakes. And as I have learned from experience, the key to life isn’t the mistakes we make, it’s how we choose to handle them.”

Haley denies any infidelity. “I have been 100% faithful to my husband throughout our 13 years of marriage,” she said in a statement, per NBC affiliate WIS-TV. “This claim against me is categorically and totally false.” Haley added that Folks’ allegations was “South Carolina politics at its worst” — although Folks’ blog reportedly has been very favorable toward Haley’s candidacy.

In the June 8 GOP primary, Haley is taking on state Attorney General Henry McMaster, Rep. Gresham Barrett, and Lt. Gov. Andre Bauer.

Of course, it was the term-limited Sanford’s affair with an Argentina woman that essentially rendered him a lame-duck governor.