When the Heritage Foundation set up shop in a red-brick Capitol Hill townhouse more than three decades ago, it represented the cutting edge of conservative thought. Ronald Reagan himself once lauded it as “that feisty new kid on the conservative block.”

Now, as the think tank hands over its leadership to Sen. Jim DeMint (R-S.C.), a tea party icon known more for his confrontational political style than his policy chops, the question is whether Heritage can catch up to the movement it once helped lead.

The changing of the guard comes at a crucial moment, when conservatism itself is gripped by self-doubt and angst in the wake of back-to-back Republican presidential defeats.

“This organization is in a position to do more to save our country than any other organization I’m aware of,” DeMint told more than 200 Heritage staff members shortly after it was announced that he would succeed Edwin Feulner, who co-founded Heritage in 1973 and has served as president for the past 36 years.

“I believe that we have put together here the power, the muscle, the ideas to turn things around,” DeMint added.

Measured in dollars, that muscle is enormous. According to Heritage’s financial report, the foundation brought in nearly $70 million last year.

And Heritage remains deeply embedded in the DNA of the Republican establishment. Nearly half of the advisers to Mitt Romney’s presidential effort were former or current Heritage scholars — among them Lanhee Chen, the campaign’s policy director.

But the intellectualism that was once the Heritage hallmark has become somewhat suspect in an era in which the insurgent passion of the tea party sets the terms of political activism.

During the 2012 presidential campaign, for instance, Heritage was often cited as the originator of a concept that most conservatives now find heretical — the “individual mandate” in the Obama health-care law requiring people to buy insurance coverage if they do not receive it from their employers or government programs such as Medicare and Medicaid.

Heritage had already begun to retool its brand for the tea party era by setting up a separate political and lobbying arm it called Heritage Action for America.

That activist effort has received mixed reviews. Many congressional Republicans were dismayed when it put out a scorecard dinging them for being insufficiently conservative for what the lawmakers regarded as relatively insignificant votes.

DeMint, on the other hand, scored a near-perfect 99 percent rating by Heritage Action — the highest of any senator.

The selection of DeMint to head the foundation “kind of moves Heritage firmly into the anti-establishment, conservative, populist side of the equation,” said Craig Shirley, a Reagan biographer. “It’s going to push that argument that the party needs to have with itself.”

In an interview, DeMint said that by taking the job, he was also taking a side in that argument.

“The election showed me that my party was not doing a good job and that we weren’t going to win another national election until we got control of our message,” DeMint said.

“We need to separate the conservative movement from the Republican Party,” he added. “We didn’t do a good job. It wasn’t a failure of conservative ideas; it was a failure of the Republican Party.”

Heritage is not the only conservative organization to face an identity crisis during this turbulent political season.

Earlier this week, former House majority leader Richard K. Armey left the conservative tea party group FreedomWorks during an internal dispute over its future direction.

And in March, the billionaire brothers Charles and David Koch filed a lawsuit seeking control of the libertarian Cato Institute, which they helped establish and fund. The legal dispute was resolved after Edward H. Crane, Cato co-founder and its only president since 1977, agreed to step down.

Though Feulner had long ago signaled his desire to relinquish the day-to-day operation of the Heritage Foundation, many had expected his successor to be David Addington, who had served as chief of staff to former vice president Richard B. Cheney and who had joined the foundation’s top ranks in May.

DeMint’s selection is likely to be popular with many of the foundation’s conservative financial backers, particularly the legions of small donors who contribute in response to its direct-mail solicitations. But it remains to be seen whether he has the temperament or connections required to manage many of its bigger benefactors.

“Bringing DeMint in makes more ideological sense than others, including David Addington,” said James McGann, director of the Think Tanks and Civil Society Program at the University of Pennsylvania.

“But that might not be best for Heritage in the long run,” McGann said. “Feulner has a long history of strong relations with Heritage donors, his senior staff and Washington political elite, and it’s not clear DeMint has those same qualities outside of his time in the Senate.”

Alice Crites contributed to this report.