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 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.
"This platform is a much bigger megaphone than he has as the junior senator from South Carolina," said John Ullyot, a former Senate Republican aide. The Heritage Foundation was never seen as centrist, Ullyot said, "and this could signal an even farther turn to the right by Heritage."
"That is not necessarily where many Republicans think the party should be going," said Ullyot, who worked for moderate GOP senators John Warner of Virginia and Arlen Specter of Pennsylvania.
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 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.
EDITOR'S NOTE — Charles Babington covers politics and Congress for The Associated Press. Follow him on Twitter: https://twitter.com/cbabington .