COLUMBIA, S.C. — Republican U.S. Sen. Jim DeMint, a favorite among tea party activists, said today he is resigning to take the helm of a conservative think tank.

The South Carolina lawmaker said in a statement he was stepping down to become president of the Heritage Foundation. His office said he would take the new job effective Jan. 1.

DeMint was first elected to the Senate in 2004 and easily re-elected six years later. He previously served in the U.S. House of Representatives for three terms.

“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,” DeMint said in a statement.

Republican Gov. Nikki Haley will appoint DeMint’s successor. She didn’t immediately signal who she might choose, or whether she would appoint herself.