The driving force behind DeMint’s ouster, according to multiple sources close to the organization, was Mike Needham, the CEO of Heritage Action for America, the organization’s political arm. Needham, these sources say, made a power play to push DeMint out, and is appealing to both pro- and anti-Trump elements to accomplish it.

"Needham has been laying the groundwork for this for two years," said a source close to Heritage. "He's been badmouthing DeMint to board members for a long time. He's got his sights set on taking over the whole thing eventually." According to a senior Republican congressional aide, Needham has been “trashing” DeMint to board members and saying that people in the White House and Congress prefer to deal with him rather than DeMint.

Multiple people close to the situation called DeMint's ouster a "coup," and said the driving force behind it was not philosophical but old-fashioned ambition and power politics. "This is an old-as-time story," said one source.

But nowadays, it’s difficult for a conflict like this on the right to unfold outside the context of ideological friction over Donald Trump and his nationalist agenda. Several people familiar with Needham's jockeying said he has successfully exploited the growing philosophical tensions on the American right—and, specifically, on the board of Heritage—to get his way.

To the Trump-averse elements on the board, Needham has pointed to DeMint's growing coziness with the new administration as evidence that the think tank, a beacon of movement conservatism, needs a new steward. At the same time, Needham has been telling pro-Trump board members like Rebekah Mercer that Heritage needs a leader who will follow the president's lead—even going so far as to float White House chief strategist Steve Bannon, a key Mercer ally, as a potential future president, according to one source.

Heritage’s tolerance of Trump has sparked some criticism in conservative circles. As a 501(c)(3) nonprofit, the Heritage Foundation can’t endorse candidates, but DeMint met with then-candidate Trump in March 2016 and avoided publicly criticizing him throughout the campaign. Heritage played a key role in guiding Trump’s transition, helping to staff many administration posts.

“There are board members who think it got too political,” said the senior congressional aide. Needham, the source said, has been doing some “pretty deft political maneuvering if you ask me. Telling each faction what they want and need to hear.”

Needham, echoed another senior Republican congressional aide, is “basically telling different board members what they wanted to hear.”

A Heritage employee concurred. “What I’ve learned is that Mike Needham will tell these board members whatever they want to hear as long as it gets them to be opposed to DeMint,” the employee said.