Jim DeMint was on the verge of being where every senator longs to be — holding a top position on an influential committee with oversight of industries critical to his state.

But, as is so often the case with the maverick from South Carolina, DeMint turned his back on convention. Instead he announced Thursday that he would resign to become president of the Heritage Foundation. The move puts De­Mint at the head of the most prominent conservative nonprofit organization in Washington and in a position he hopes will afford more power to move the Republican Party in an ever-rightward direction.

“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, 61, said in a statement.

DeMint’s decision marks a monumental change from a not-so-long-ago era when abandoning a prime perch in the Senate to head a think tank would have been unthinkable. But the past decade has shown the influence that figures outside of elected office — whether tea party leaders or anti-tax advocate Grover Norquist — can have on the conservative movement.

“It’s a creative, innovative move, and demonstrative of the newer way of thinking about how to use new tools today to move an agenda, where service in government is just one way, but not the only way, to drive the conversation,” said Eric Ueland, a former Senate chief of staff and now a lobbyist with the Duberstein Group.

“The landscape has changed,” added Sen. John Cornyn (R-Tex.), who jousted with DeMint over endorsements of Republican Senate candidates. “The influence of the political parties has been diminished with the rise of super PACs and other people who decide to get involved.”

DeMint’s job at Heritage will almost certainly come with a great deal more money than his $174,000 Senate salary. The terms of his deal are unknown, but the man DeMint will replace, Edwin Feulner, makes more than $1 million a year.

DeMint’s move is part of a reordering of the Republican Party after an election in which the GOP could not gain the presidency and lost seats in the Senate and House. Earlier this week, former Republican House majority leader Richard K. Armey stepped down from FreedomWorks, an influential group aligned with the tea party movement. And in the House, Speaker John A. Boehner (R-Ohio) kicked a few conservative lawmakers off prominent committees in an effort to consolidate power.

DeMint retires from the Senate having exerted an enormous amount of influence on the institution — yet without ever having passed a single piece of significant legislation.

Rather than rising up the Senate ranks to influence legislation, DeMint chose to be a cheerful starter of civil wars. With his Senate Conservatives Fund, De­Mint assembled candidates and money to wage primary fights against establishment Republicans he deemed insufficiently conservative. He experienced both spectacular success and failure.

DeMint helped create a new brand of tea party senator, focused on shrinking the federal government, cutting spending and supporting conservative social causes, what Sen. Rand Paul (R-Ky.) hailed Thursday as the “liberty caucus.” Paul’s 2010 primary victory upended an establishment pick supported by Minority Leader Mitch McConnell (R-Ky.).

Among DeMint’s biggest victories were the elections of Sen. Marco Rubio (R-Fla.) in 2010 and Sen.-elect Ted Cruz (R-Tex.) this year. “Jim DeMint was the first person in Washington that believed in me,” Rubio said Thursday in a statement.

But DeMint also helped elevate doomed candidates, such as Sharron Angle in Nevada, Christine O’Donnell in Delaware and Ken Buck in Colorado, who lost races that establishment alternatives were favored to win.

DeMint, a native of Greenville, S.C., worked in business before he was elected to the House in 1998. In 2004, he won the Senate seat vacated by retiring Democrat Ernest F. Hollings, a change that reflected South Carolina’s broader political shift from bastion of the Democratic “Solid South” to epicenter of a deep-red modern conservatism.

In the Senate, DeMint has been distinguished by his strident attacks on Democrats: For example, he predicted the health-care debate would be President Obama’s “Waterloo.” His key accomplishments were in blocking legislation. He infuriated colleagues by using parliamentary procedures to force weekend votes, even if he didn’t show up for the actual roll call himself.

His most recent move was to publicly oppose Boehner’s GOP offer to Obama calling for $800 billion in increased tax revenue — which DeMint labeled a “charade” that sold out conservative principles.

DeMint was positioned to become the ranking Republican on the Commerce, Science and Transportation Committee next year, a post that he could have used to boost his coastal state’s shipping industry and its bid to deepen Charleston’s port.

Longtime senators found De­Mint’s move part of a puzzling trend away from working inside the institution. “People have different mind-sets, and they have different goals. Some people come up for a term or two terms or a term and a half and leave and go on to different things. Some ­people come up to be long-distance runners, to make a difference, to work within the institution,” said Sen. Richard C. Shelby (R-Ala.), a 26-year veteran who has chaired two committees and is about to become the top Republican on another.

But tea party activists hailed DeMint’s move.

“I was shocked, and at first I said, ‘Oh, no,’ but then I said, ‘Wait a minute, let’s think about this,’ ” said Joe Dugan, chairman of the Myrtle Beach Tea Party in South Carolina. “The Heritage Foundation is a tremendous organization, and as president of it he will have a broad, broad platform to educate people across the country about conservative ideas and ideals. And that’s what the country needs.”

Other Republicans, such as former South Carolina congressman Bob Inglis, think what the party needs is a little less of DeMint’s rigidity.

Inglis had been a friend of DeMint, but DeMint declined to endorse him in a 2010 primary fight against a former prosecutor, Trey Gowdy, whose politics were closer to DeMint’s.

That strategy may work in South Carolina, Inglis said Thursday, but poor Senate nominees have cost Republicans about five seats and a possible 50-50 deadlock in the chamber next year — as opposed to holding just 45 seats come January.

“We’ve got to get into the business of addition and multiplication, and out of the business of subtraction and division,” Inglis said. “Because it ain’t working out for us.”

South Carolina’s governor, Nikki Haley (R), will appoint a replacement for DeMint who will serve until the next general election, in 2014. Many GOP leaders favor Rep. Tim Scott (R), 47, because he is a reliable conservative from the House freshman class of 2010 and also is an African American who might help extend the party’s appeal beyond its base of older, white voters.

A Scott appointment would be a remarkable turn for a state that sent onetime segregationist leader Strom Thurmond to the Senate for 48 years.

DeMint, elaborating on his decision in a Thursday interview with radio host Rush Limbaugh, blamed GOP losses in November on conservatives failing to more aggressively communicate their ideas.

“I think the problem is, as conservatives, we have not taken enough control of our message and our ideas and communicated them directly to the American people,” he told Limbaugh. “That’s what we want to do at Heritage.”

Chris Cillizza, Amy Gardner, Sean Sullivan, Rachel Weiner, Ed O’Keefe, Philip Rucker and Aaron Blake contributed to this report.