Sen. Jim DeMint (R-S.C.), a tea party favorite, is leaving Congress next… (Win McNamee, Getty Images )
WASHINGTON — The surprise resignation of Republican Sen. Jim DeMint of South Carolina on Thursday could prove to be a marker for a decline in the influence of the tea party movement he has helped lead.
His departure from Congress, effective next month, comes as the political winds appear to be blowing against the 61-year-old lawmaker and the movement he has spoken for. Some of the movement's most fiery members lost reelection bids last month, including Reps. Allen West of Florida, Joe Walsh of Illinois and Chip Cravaack of Minnesota. Earlier this month, the House GOP leadership unceremoniously removed three conservatives from key committee assignments.
And polls have shown declining support for the movement. A wide survey in DeMint's very conservative home state, released this week, found that more South Carolinians now disapprove of the tea party movement than approve of it. Even among the state's Republican voters, fewer than 1 in 12 said they considered themselves tea partyers, according to the Winthrop University poll.
"This may be an indication that the movement is truly waning," said Jennifer Duffy, an analyst with the independent Cook Political Report. "This should also be frustrating" for DeMint.
DeMint, who sought to carve out an influential role as the leader of the Republican right in the Senate, will take over in April as president of the Heritage Foundation, a conservative think tank based in Washington. In a statement, he said he was "leaving the Senate now, but … not leaving the fight." Later, he joked during an appearance before the foundation staff that his new job was "a big promotion," according to an account on the Heritage website.
DeMint positioned himself as an unyielding foe of Republican efforts to compromise with President Obama over government spending, aggressively opposed efforts to provide a pathway to citizenship for millions of undocumented immigrants, and alienated at least some Republican colleagues by threatening to back primary challenges against those who deviated from conservative positions.
On Tuesday, he criticized a proposal by House Speaker John A. Boehner (R-Ohio) to raise $800 billion in additional tax revenue, made as part of negotiations designed to avert spending cuts and increased taxes that would otherwise take effect next month. DeMint said Boehner's "tax hike will destroy American jobs and allow politicians in Washington to spend even more."
DeMint's influence was at its zenith last year during the Republican presidential primary contest, in which tea party sentiment helped push Mitt Romney and other contenders to the right. Hoping to gain his endorsement, five presidential candidates, including Romney, flew to Columbia, S.C., to court the senator, answering his questions at a nationally televised Labor Day forum that he organized.
But Republican losses in the election weakened his position. The party had hoped to win control of the Senate, but instead lost ground. DeMint played a role in some of the worst defeats. He embraced the candidacy of Todd Akin, even after the Missouri congressman's controversial remark about "legitimate rape" sent the Republican establishment fleeing. And in Indiana, he provided financial support for Richard Mourdock, a conservative who ousted longtime Republican Sen. Richard G. Lugar in the GOP primary but proved too extreme for voters in the general election.
Similarly, in 2010, DeMint provided endorsements and financial encouragement for Sharron Angle of Nevada and Christine O'Donnell of Delaware, both tea-party-backed candidates for the Senate who lost to Democrats.
On Thursday, tea party leaders pushed back against the notion that their movement was in decline. Republican Sen. Patrick J. Toomey of Pennsylvania, who took over for DeMint as chairman of the influential Senate Republican Steering Committee, said he did not see the end of the line for the tea party.
"We had a number of terrific advocates for limited government and freedom who won elections to the Senate — Ted Cruz and Jeff Flake and Deb Fischer," Toomey said. "The cause is still strong."
South Carolina Gov. Nikki Haley, a Republican, will appoint DeMint's successor, to serve until the 2014 election, when voters will fill the remaining two years of the senator's term. Speculation about DeMint's replacement centered on a cadre of young conservative Republican congressmen, including Rep. Tim Scott, who was reported to be DeMint's choice and would be the only African American member of the Senate if chosen.
DeMint's decision could also open the way for him to run for the GOP presidential nomination. As recently as last month, he had refused to discuss a 2016 candidacy, saying only that he wasn't ruling anything out.
In the meantime, his decision to join the Heritage Foundation could provide a measure of financial security for a man who is among the least wealthy members of the Senate, according to financial disclosure reports. His predecessor, Edwin J. Feulner, who helped found Heritage in the 1970s, was paid more than $1 million in 2010, according to the foundation's most recent filing with the Internal Revenue Service.
Lisa Mascaro, Kathleen Hennessey and Morgan Little in the Washington bureau contributed to this report.