WASHINGTON — Not long after Jim DeMint took over the Heritage Foundation last spring, his team summoned the staff for a meeting unlike any the decorous conservative policy organization had ever convened. Music blared in the auditorium. Policy analysts began with a few awkward jokes and then scampered about in a series of skits that laid out the foundation’s goals.

Some of the veteran managers of the staid think tank stared on balefully. A new era had arrived.

From its inception in 1973, the Heritage Foundation has provided the blueprint for the Republican Party’s ideas in Washington. In doing so, it has proved to be the most durable organization of its kind.

But under Mr. DeMint, a South Carolinian who gave up his Senate seat last year to take the helm, Heritage has shifted. Long known as an incubator for policy ideas and the embodiment of the party establishment, it has become more of a political organization feeding off the rising populism of the Tea Party movement.

“Politics follows the culture,” Mr. DeMint said in an interview. “The conservative movement has been derelict in not putting together an organized movement across this country.”