Beloved by conservatives and often derided as a nuisance by his foes, South Carolina Sen. Jim DeMint has always had a way of ruffling feathers.

Now he will be doing the same, but from outside the Senate – from a perch free of seniority rules, powerful leadership structures and procedural quirks.

DeMint announced Thursday that he will be leaving the Senate in January to head the Heritage Foundation think tank, becoming what one senior Republican describes as the "CEO of the conservative movement." DeMint leaves behind a mixed record of success in bolstering the ranks of Tea Party-minded senators, but his legacy of influencing the direction of the GOP is likely far from over.

NBC's Chuck Todd and Kelly O'Donnell discuss the departure of Tea Party favorite from the US Senate, and possible replacements South Carolina Gov. Haley could pick.

In a statement announcing his surprising departure, DeMint hinted at a leadership vacuum in the ideological branch of the party that he's helped shape since his election to the Senate in 2004. "I've decided to join The Heritage Foundation at a time when the conservative movement needs strong leadership in the battle of ideas," he wrote. "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 even more effective in the years to come."

"Your effect on the inside sometimes is limited, especially when you challenge the leadership a lot. And Jim DeMint has brushed up against GOP leadership," noted Family Research Council head Tony Perkins. "I think he will be one who can rally conservatives on the outside and -- with an understanding of the inside process -- will be very effective in helping lay strategies for the conservative movement."

"It's an opportunity to develop policy and be in the leadership of the thought development of the movement without having to take into consideration some of the internal dynamics of the Senate," said Colin Hanna, president of conservative organization Let Freedom Ring. "I know from conversations with him that he's eager for an opportunity to develop ideas outside of the context of the leadership dynamics of a very complex body."

South Carolina Senator Jim DeMint announced he is leaving Congress to become a full-time political activist as president of conservative research group the Heritage Foundation. NBC's 'Meet the Press' moderator David Gregory reports.

The Heritage Foundation, founded in 1973 and situated just blocks from the U.S. Capitol, has been one of the flagship institutions of the conservative movement, churning out volumes of public policy proposals from hundreds of experts.

Never reputed for his affability, DeMint's new role outside the Senate offers quiet relief to some colleagues who found the stalwart conservative's tactics abrasive. In July 2007, for example, DeMint used Senate rules to force members to vote on a Saturday, then further enraged them by failing to show up in the Capitol for the vote itself. Lawmakers grumbled, sometimes publicly, about his opposition to the entrenched GOP lawmakers he helped defeat. He scored a major victory by winning support for a 2010 earmark ban, but only after battling intense behind-the-scenes opposition from Minority Leader Mitch McConnell.

The move will also allow him to step away entirely from the daily routine of roll call votes and constituent work, focusing instead on efforts to nurture fresh ideas and develop new leaders for a wing of the GOP under mounting, post-election pressure to pipe down.

That's not to say DeMint's rally cries have always been heeded.

Alex Wong / Getty Images Sen. Jim DeMint talks on the phone in his office December 6, 2012 on Capitol Hill in Washington, DC.

Famed for his willingness to forfeit immediate political power in favor of uncompromising values, DeMint famously declared after Republican losses in 2008 that he would "rather have 30 Republicans in the Senate who believe in the principles of freedom than 60 who don’t believe in anything."

That philosophy earned him a roller coaster record as a kingmaker in dozens of GOP primary endorsements made during his political career. As one of the most consistently conservative members of the upper chamber, DeMint recorded both landscape-changing victories, such as the successes of upstart candidate Marco Rubio in Florida in 2010, as well as humiliating failures like the defeat of widely parodied Senate contender Sharron Angle in Nevada.

In 2010 and 2012, DeMint backed several candidates who went on to win Senate seats and serve as lauded conservative luminaries, like Rubio, Paul and Mike Lee as well as senator-elect Ted Cruz.

But in both cycles, he also backed a number of candidates who either lost their GOP Senate primaries or went on to lose the general election. The 2010 list includes New Hampshire's Ovide Lamontagne, California's Chuck DeVore and Indiana's Marlin Stutzman (who lost their 2010 primaries), as well as Delaware's Christine O'Donnell, Colorado's Ken Buck, and Angle, who were defeated by Democrats in the general election.

In 2012, he supported eventual losers in Indiana's Richard Mourdock, as well as Missouri candidate Todd Akin, whose remarks about "legitimate rape" turned a potentially competitive general election race into a trouncing.

Sen. John Barrasso, R-Wyo., shares his reaction to Sen. Jim DeMint's retirement and plans to take a position at the Heritage Foundation. Barrasso explains how the retirement will affect the Senate and also talks about the state of fiscal cliff negotiations.

The Senate Conservatives Fund -- a fundraising engine DeMint founded and later cut ties with in order to pursue a super PAC -- contributed to a total of 20 candidates during the 2010 and 2012 cycles. Of those candidates, 15 went on to win their primary contests, while eight won their general election contests. (One of those victorious general election candidates - Nebraska's Deb Fischer - won the group's support after its first pick lost to her in the state's Republican primary.)

Supporters of DeMint note that GOP candidates backed by DC insiders have also suffered their share of general election defeats and that DeMint's successfully elected proteges include some of the most lauded young conservatives in the Senate today.

"When you take a risk and you go out and you back a principled candidate, yes, sometimes you lose," said Perkins. "There are factors beyond your control and you don't always win, but the Senate is a much different place today because Jim DeMint was willing to take some risks."

In addition to his backing of controversial candidates, he has been no stranger to media backlash himself.

He was blasted in 2007 for saying that al-Qaida recognized "wimps" in Congress, adding "I believe a lot of the casualties can be laid at the feet of all the talk in Congress about how we’ve got to get out, we’ve got to cut and run." As early as his first run in 2004, he was pressured to apologize after saying that gay people should not teach in public schools.

In 2009, he urged Republicans to defeat the Obama-backed health care bill, declaring "If we’re able to stop Obama on this, it will be his Waterloo. It will break him."

NBC's Chuck Todd contributed reporting.