WASHINGTON — Sen. Jim DeMint, the conservative Republican from South Carolina who helped ignite the Tea Party movement, will leave the Senate to become president of the Heritage Foundation, a conservative research group.

DeMint - who has fashioned himself into a bit of a kingmaker for conservative Republicans, often at the expense of his own Republican colleagues - now finds himself with a comfortable and well-paying perch that will provide a platform to continue hisefforts to push the Republican Party to the right.

His imminent departure will allow him to advocate even more loudly against a big budget deal that includes higher tax revenue sought by President Barack Obama. He has been among the biggest critics of a deal proffered by House Speaker John Boehner to address the impending fiscal crisis by generating at least $800 billion in new tax revenue.

“I’m leaving the Senate now, but I’m not leaving the fight,” DeMint said in a prepared statement Thursday. “I’ve decided to join The Heritage Foundation at a time when the conservative movement needs strong leadership in the battle of ideas. No organization is better equipped to lead this fight, and I believe my experience in public office as well as in the private sector as a business owner will help Heritage become evenmore effective in the years to come.”

DeMint will depart the Senate in January. He replaces Edwin Feulner, 71, who will continue part-time as chairman of the foundation’s Asian Studies Center.

A hero to many Republicans for his fundraising abilities, DeMint frustrated Senate colleagues by backing Republican candidates such as Sharron Angle of Nevada in 2010 and Richard Mourdock of Indiana this year, contenders who proved too conservative to be elected statewide. The losses by Angle and Mourdock and other candidates endorsed by DeMint hurt Republicans in the past two elections in their efforts to retake the Senate, although he successfully backed conservative candidates in Florida, Texas and Utah.

“The truth is that Jim De-Mint’s philosophy on everything from Medicare to women’s reproductive rights, as embodied by his handpicked candidates for Congress, has been rejected by voters,” said Sen. Patty Murray of Washington, who headed the Democratic Senatorial Campaign Committee this year.

The costly Senate defeats, as well as DeMint’s proclivity for gumming up legislation on the floor, stunted his chances for leadership in the Senate, and his influence may well be enhanced from the outside.

Gov. Nikki Haley of South Carolina, a Republican, will now be compelled to appoint a successor who would then run to maintain the seat in a special election in 2014, when Republican Sen. Lindsey Graham, the senior senator from the state, will also be up for re-election. Aides said Haley was surprised by DeMint’ssudden announcement.

South Carolina is a small state, politically speaking, and almost every Republican member of the House delegation, many of them close to DeMint politically and personally, are possible fill-ins.

Rep. Tim Scott is a popular freshman from Charleston who is well known around the state from his year in the South Carolina General Assembly. The first black Republican to serve his state since Reconstruction, Scott could give Republicans a high-profile black member in the Senate, which currentlyhas no black member from either party. Scott is believed to have other ambitions, including a possible run at the governor’s mansion.

Haley could also look to Rep. Mick Mulvaney, also a freshman, whose politics align closely with DeMint but who is viewed by House Republican leadership as less of an obstructionist, even as he often votes against itsleaders. Mulvaney is among the more active members of his delegation and House freshmen. But, unlike Scott, Mulvaney has no pre-existing relationship to Haley in a job and state where relationships matter, making Scott perhaps a more likely choice.

DeMint, “has served South Carolina and the national conservative movement exceptionally well,” Haley saidin a statement. “His voice for freedom and limited government has been a true inspiration. 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.”

Rep. Trey Gowdy, another South Carolina freshman, saidhe was not interested.

“I know Gov. Nikki Haley will make the decision that is best for South Carolina,” he said in a statement, “and I pray the Lord will give her wisdom. There are scores of talented women and men in South Carolina who are qualified to be considered. I hope she will consider my four congressional colleagues Tim Scott, Mick Mulvaney,Jeff Duncan, or Joe Wilson.”

The distraction of a new seat may well save Graham, who has taken some positions that have drawn fire in his conservative state. Graham told a local radio station Thursday that when DeMint, whom he called “irreplaceable in many ways,” told him the news, he said “don’t tell me what you’re about to tell me.”

Front Section, Pages 3 on 12/07/2012