THE SURPRISE JOB change by the Senate's most prominent tea partyer will complicate Republican moderates' bid to nudge their party toward the center after another stinging campaign loss.

Sen. Jim DeMint, of South Carolina, is giving up his high profile in the Senate, where he annoyed establishment Republicans and delighted conservative purists. But he may play an even broader role in the nation's political debate in his new post as president of the Heritage Foundation, Washington's best-known conservative think tank.

"There was already going to be a vigorous debate over the future of the Republican Party," said Dan Schnur, a former top GOP aide who now teaches political science at the University of Southern California. "This is just going to make that debate more vigorous."

DeMint, a founder of the Senate Tea Party Caucus, takes hard-line stands on issues that many mainstream Republicans say need a lighter touch from a party whose white conservative base is shrinking.

Take immigration. Republicans are losing the fast-growing Hispanic vote. That's partly because their stands on illegal immigration strike many people as overly harsh and dismissive of all Latinos, including U.S. citizens.

During George W. Bush's presidency, DeMint helped lead the fight against GOP-crafted efforts to create paths to legal status for illegal immigrants.

Tax and spending policies? DeMint last week attacked Republican House Speaker John Boehner's compromise deficit-reduction bid to generate $800 billion in new tax revenues over 10 years. That's half the amount President Obama seeks.

Many Republicans see Boehner's plan as the best possible outcome, given Obama's re-election last month. DeMint says that the plan would "destroy American jobs and allow politicians in Washington to spend even more."

That's the sort of uncompromising stand that has made DeMint a tea-party hero and one of the few senators who might be widely recognized outside his home state. It also makes him a deeply frustrating figure to Washington officials who say that compromise is essential in an evenly divided nation with a Democratic-led Senate and Republican-controlled House.

DeMint may be best known for backing tea-party activists for Senate seats, often infuriating the Republican establishment. His 2010 support for Marco Rubio in Florida, Rand Paul in Kentucky and Mike Lee in Utah had happy results. But detractors say that DeMint hurt the party by backing eventual losers such as Christine O'Donnell in Delaware, Ken Buck in Colorado and Sharron Angle in Nevada.

DeMint was unbowed, saying that he would rather have "30 Republicans in the Senate who believe in principles of freedom than 60 who don't believe in anything."

Heritage's choice of DeMint comes at a moment of uncertainty and unrest for conservative activists. Facing the looming "fiscal cliff" of big tax increases and spending cuts, a growing number of GOP lawmakers say that they are willing to break a pledge never to vote for tax increases. That's a setback for prominent anti-tax advocate Grover Norquist.

Former House Majority Leader Dick Armey, R-Texas, took an $8 million payout to leave the tea-party group FreedomWorks after a dispute over its future direction.

Now DeMint is leaving the Senate for a much- better-paying job with a foundation that's highly regarded in conservative circles.

Unless DeMint softens his views, he's poised to be a powerful opponent of those trying to move the Republican Party toward the middle.

In a 2010 Wall Street Journal opinion piece, DeMint told newly elected senators with tea-party ties that they "must now overcome determined party insiders if this nation is going to be spared from fiscal disaster."

"People will try to convince you to moderate conservative positions and break campaign promises, all in the name of winning the next race," DeMint wrote. "Resist the temptation to do so."

He added: "The word 'senator' before your name carries plenty of clout. All senators have the power to object to bad legislation, speak on the floor and offer amendments."

Following a disappointing election in which Republicans lost the presidential race and failed to retake the Senate, DeMint is giving up that power. In exchange, he's getting a big platform and megaphone that can help him resist efforts to move his party in a direction that many campaign strategists believe it needs to go.

Charles Babington covers politics and Congress for the Associated Press.