"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. "My constituents know that being a Senator was never going to be my career."
The senator, a vocal advocate for term limits, had already pledged not to seek a third term.
South Carolina Gov. Nikki Haley (R) will appoint DeMint's successor, who will serve until a 2014 special election. That means two Senate races in the Palmetto State that year. Sen. Lindsey Graham (R) -- targeted by many of the conservatives who love DeMint -- is up for reelection. DeMint's surprising move appears to be a break for Graham, who may see potential primary rivals flock to the open seat instead of challenging him.
Before entering politics, DeMint worked in market research, and he told the Journal that he's excited about taking Heritage Foundation research and working to "translate those policy papers into real-life demonstrations of things that work."
Heritage Chairman of the Board Thomas A. Saunders, in a statement, praised DeMint's "passion for rigorous research, his dedication to the principles of our nation’s founding, and his ability to translate policy ideas into action."
DeMint will take over from Ed Fuelner, who helped found the Heritage Foundation in 1973 and has been its president since 1977.
In 2010, Fuelner earned a total compensation (including bonuses and incentives) of $1,098,612. His base salary was $477,097. The annual salary for a senator: $174,000. (DeMint happens to be one of the poorest members of the Senate. According to the Post's Capitol Assets investigation, his estimated wealth in 2010 was $40,501.)
“I couldn’t be more pleased with the Board’s selection,” said Feulner in a statement. “Jim DeMint understands that conservative principles and values advance the interests of all Americans — regardless of age, gender, wealth or race."
The current president will stay on as chancellor of the foundation and chairman of Heritage's Asian Studies Center.
DeMint phoned McConnell this morning to tell him the news, according to leadership aides.
In a statement, McConnell thanked DeMint “for his uncompromising service to South Carolina and our country in the United States Senate.
"Jim helped provide a powerful voice for conservative ideals in a town where those principles are too often hidden beneath business as usual," McConnell added. "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."
In his new role, DeMint will serve as the boss of McConnell’s wife, Elaine Chao, the former labor secretary who is a Heritage distinguished fellow.
McConnell’s deputy, Sen. Jon Kyl (R-Ariz.) appeared caught off-guard by the announcement. “I just heard about it,” he told reporters outside his office.
DeMint's political allies were quick to congratulate the senator.
Republican Study Committee Chairman Jim Jordan (R-Ohio) said it was "disappointing" to lose a fellow conservative in Congress, but "South Carolina’s loss is the country’s gain.”
“Senator DeMint has done more to advance the cause of freedom and liberty in Congress than anyone else since his election,” said Chris Chocola, president of the anti-tax Club for Growth, in a statement. “We wish him nothing but the best in his new role at Heritage.”
DeMint has helped elect a number of like-minded colleagues in recent years through the now-independent Senate Conservatives Fund -- including Texas Sen. Ted Cruz, Utah Sen. Mike Lee, Kentucky Sen. Rand Paul and Florida Sen. Marco Rubio.
Aaron Blake and Ed O'Keefe contributed to this report.
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