Unless you’re a dedicated policy wonk, the name Stuart Butler probably doesn’t ring a bell. For 35 years, Butler has been a senior researcher at the conservative think tank Heritage Foundation. He was among the most visible figures — possibly the( most visible — shaping conservative views on social policy. Last week, Butler disclosed that he is moving to the left-leaning Brookings Institution.

Holy cow!

I admit to being surprised, even stunned. It’s as though Derek Jeter decided to play for the Red Sox or Vladimir Putin became secretary general of the United Nations. The move is totally counterintuitive.

There’s no indication that Butler’s views have changed. He has criticized the Affordable Care Act (Obamacare), advocated cuts in Social Security and doubted the effectiveness of many welfare policies. Indeed, Brookings boasted in a press release that Butler’s arrival shows open-mindedness. It “underscores our interest in encouraging a diversity of views,” said Ted Gayer, vice president and director of the Economic Studies program for Brookings.

Brookings’s veneer is undeniably middle-of-the-road liberal. President Strobe Talbott was deputy secretary of state in the Clinton administration; economist Alice Rivlin, one of its better known scholars, headed the Office of Management and Budget under Clinton. In part, Butler’s shift reflects his low-key personality. He has never been a take-no-prisoner ideologue. In the past, he has worked with Rivlin and Brookings scholar Isabel Sawhill to try to find common ground on the budget.

According to Butler, Brookings approached him last fall. It was less disaffection with Heritage than the appeal of working with a new group of people — many longtime friends and debating partners — that caused him to accept. “There’s a logic for me to take conservative ideas to different audiences,” he said.

I suspect that there’s a bit more to his move.

Most think tanks were once idea factories. They sponsored research from which policy proposals might flow. In the supply chain of political influence, their studies became the grist for politicians’ programs. But think-tank scholars didn’t lobby or campaign. Politicians and party groups did that. There was an unspoken, if murky, division of labor. This was Butler’s world.

But it’s disappearing, and many think tanks — liberal and conservative — have become more active politically. They are now message merchants, packaging and merchandizing agendas for a broader public. Heritage has long been aggressive in peddling its message and has become more so. In 2010, it created an affiliate — Heritage Action — that lobbied and mobilized grass-roots conservatives. In this world, I surmise, Butler’s role is diminished. By contrast, Brookings remains a bit more traditional.

Sociologist Tom Medvetz at the University of California, San Diego, and author of the recent book “Think Tanks in America” makes a similar point. I e-mailed Medvetz for a reaction, and here’s his partial response:

“To my mind, the selection of Jim DeMint as president points to a larger shift at Heritage toward prioritizing activism and fundraising over intellectual work. [DeMint, a former senator from South Carolina, became Heritage’s head in 2013.] . . . DeMint’s selection was important because it gave the organization more legitimacy among conservative activists, including those in the tea party. DeMint also strengthened Heritage’s ties to Capitol Hill. . . . I think it’s inevitable that this kind of change would alienate the most scholarly figures at Heritage.”

What’s occurring is a subtle change to a major American institution. Heritage is not alone. To varying degrees, other think tanks face similar pressures. They will probably do less thinking and more politicking and self-promotion.

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