South Carolina Republican U.S. Sen. Jim DeMint is resigning his post to become the next president of the Heritage Foundation.

DeMint announced this morning he will leave the Senate at the beginning of January to become the next president of the conservative think tank.

“It’s been an honor to serve the people of South Carolina in United States Senate for the past eight years, but now it’s time for me to pass the torch to someone else and take on a new role in the fight for America’s future,” he said.

“I’m leaving the Senate now, but I’m not leaving the fight. I’ve decided to join The Heritage Foundation at a time when the conservative movement needs strong leadership in the battle of ideas.”

He added, “South Carolina has a deep bench of conservative leaders and I know Governor (Nikki) Haley will select a great replacement.

DeMint was elected to the U.S. House of Representatives in 1998. He left the House after limiting himself to three terms and then was elected to the U.S. Senate in 2004 and re-elected in 2010.

Haley issued a statement praising DeMint’s service.

“His voice for freedom and limited government has been a true inspiration,” she said. ”On a personal level, I value Jim’s leadership and friendship. Our state’s loss is the Heritage Foundation’s gain. I wish Jim and Heritage all the best in continuing our shared commitment to America’s greatness.”

DeMint’s announcement is considered a sort of “political Pearl Harbor” among state political insiders, who expected he would leave his term after it ended in 2016 — but not next month.

Speculation is rampant on who Haley might pick as a successor,including U.S. Rep. Tim Scott, or former Attorney General Henry McMaster.

Scott, who first was elected to the state’s first district in 2010, said today he would not speculate on reports that he was the leading candidate, DeMint’s favorite.

“Gov. Haley does have the only vote that counts,” Scott said. “In the end, I think she’s going to make the best decision she can through whatever process she goes through.”

Asked if he were interested, Scott brushed aside the question. “I don’t want to be coy, but I would say if she calls, I’ll give her an answer. I’m going to keep all my speculation as to what is going to happen to myself.”

Whoever is appointed would stand for re-election in 2014, the same year that both Haley and Sen. Lindsey Graham are up for re-election.

“To say I was stunned is an understatement,” Graham said today on the floor of the Senate, saying South Carolina has “lost a great strong political voice... On a personal level, I’ve lost my colleague and friend. Jim and I have known each other for almost 20 years now, and I think we’ve done a pretty good job for South Carolina.”

Under state law, Haley will name a successor to fill the seat until the election season of 2014, when a special election will be called to fill the final two years of DeMint’s six-year term.

S.C. Attorney General Alan Wilson, a Republican, said, “I was completely floored by it (DeMint’s announcement). I didn’t see it coming.”