(WNS)–U.S. Sen. Jim DeMint, the Republican from South Carolina who has led the conservative wing of the party from inside Capitol Hill, announced Dec. 6 that he is resigning his Senate seat to become the next president of The Heritage Foundation.

“I’m leaving the Senate now, but I’m not leaving the fight,” Sen. DeMint said in a statement. “I’ve decided to join The Heritage Foundation at a time when the conservative movement needs strong leadership in the battle of ideas. My constituents know that being a senator was never going to be my career.”

DeMint will leave the Senate in January and replace Ed Feulner, the longtime president of The Heritage Foundation—an influential conservative think tank located near the U.S. Capitol. Feulner envisioned the organization in 1973 as a place to research, promote, and defend conservative ideas.

The group’s board of trustees unanimously chose DeMint as Feulner’s successor. DeMint will assume the presidency on April 3 after starting with Heritage in early January as president-elect.

“Jim DeMint has shown that principled conservatism remains a winning political philosophy,” said Heritage Chairman of the Board Thomas A. Saunders in a statement. “His passion for rigorous research, his dedication to the principles of our nation’s founding, and his ability to translate policy ideas into action make him an ideal choice to lead Heritage to even greater success.”

DeMint’s move means that one of Washington’s most vocal conservatives will now be positioned on the outside of Congress. DeMint, who supported term limits and had long suggested that he would not run for a third term when his current one expired in 2016, has often clashed with his own Republican congressional leaders.

This week DeMint attacked House Speaker John Boehner’s recent proposals during the ongoing debate over pending tax increases and spending cuts. DeMint warned that Speaker Boehner’s plan would “destroy American jobs and allow politicians in Washington to spend even more, while not reducing our $16 trillion debt by a single penny.”

He added, “This isn’t rocket science,” in an example of the kind of firebombs he sometimes lobbed at the GOP establishment. “Everyone knows that when you take money out of the economy, it destroys jobs, and everyone knows that when you give politicians more money, they spend it.”

While first elected before the movement grew, DeMint quickly became a darling of Tea Party groups for his willingness to take on entrenched interests. He’d often get some of the biggest cheers at annual gatherings of conservatives such as the Values Voter Summit.

In recent years, a small group of like-minded senators have joined DeMint to form an informal group of staunch fiscal and social conservatives within the Republican’s Senate caucus. That group includes Sens. Marco Rubio of Florida, Pat Toomey of Pennsylvania, Rand Paul of Kentucky, and Mike Lee of Utah. Next year, new GOP conservative Ted Cruz of Texas will enter the Senate and join that voting block. The new face of the loyal opposition within the Senate likely will come from within this group.

“Jim helped provide a powerful voice for conservative ideals in a town where those principles are too often hidden beneath business as usual,” Senate Republican Leader Mitch McConnell of Kentucky said in a statement. “There is no question in my mind that he raised the profile of important issues like spending and debt and helped galvanize the American people against a big government agenda.”

DeMint, who ran a small business before being elected to Congress, now will try to rally a conservative movement that feels threatened after Republican losses in the November election. Meanwhile, in South Carolina, Republican Gov. Nikki Haley will appoint DeMint’s successor. That person will serve until a 2014 special election—the same year that Sen. Lindsey Graham, the Palmetto State’s other Republican senator, will be up for reelection.