But Professor Feldstein was “not a polemicist,” Mr. Summers said, and viewed himself as a scholar, not a political actor.

He was also a prolific writer, the author or editor of several books, on topics like taxes and capital formation, the Social Security system and the economics of art museums, as well as hundreds of academic papers. He frequently contributed opinion pieces to The New York Times, The Wall Street Journal, The Washington Post and other publications.

Professor Feldstein clashed at times with members of the Reagan administration and White House staff, in particular Treasury Secretary Donald T. Regan. He publicly questioned their reluctance to raise taxes to reduce the federal budget deficit and raised doubts about the strength of the recovery in the wake of the recessions of the early 1980s. He argued that economic growth alone would not erase the deficit.

At one point in early 1984, Mr. Regan pointedly distanced himself from Professor Feldstein’s annual Economic Report of the President, telling a congressional hearing that lawmakers could “throw away” the 343-page document. Mr. Regan described one of its conclusions, that the dollar was overvalued, as the product of “confused thinking.”

Mr. Feldstein maintained that the federal budget deficit was more serious than Mr. Regan and other administration economists had acknowledged, finding them too cautious about jeopardizing Reagan’s three-year tax-cut program.

“I know he butted heads with Donald Regan, though Ronald was always on his side,” N. Gregory Mankiw, a professor of economics at Harvard, who was a staff economist under Professor Feldstein at the time, said in an interview. “Marty was a deeply principled man who believed in calling it like he saw it, and that was true when he was the president’s chief economist, as a scholar and as an op-ed writer for many, many years.”