JamesL. Sundquist, a Brookings Institution scholar of politics and public policy who early in his career wrote speeches for President Harry S. Truman and was an assistant to then-New York Gov. W. Averell Harriman, died February 17, 2016 at a hospice center in Arlington, Virginia. He was 100 (Family photo)

James L. Sundquist, a Brookings Institution scholar of politics and public policy who early in his career wrote speeches for President Harry S. Truman and was an assistant to then-New York Gov. W. Averell Harriman, died Feb. 17 at a hospice center in Arlington, Va. He was 100.

The cause was complications of pneumonia, said a son, Erik Sundquist.

As a Brookings fellow from 1965 to 1985, Mr. Sundquist also spent time as director of the policy research organization’s government studies program. He was the author of books on policy-making and governance, state-federal relations, confrontations between executive and legislative branches of government, as well as a memoir of his childhood in Utah.

A former reporter for the Salt Lake City Tribune newspaper, he came to Washington in 1941 as an administrative analyst at the Bureau of the Budget and his career evolved into that of a de facto efficiency expert.

After Vice President Truman assumed the presidency following the death of Franklin D. Roosevelt in 1945, Mr. Sundquist often aided the White House by helping craft speeches.

In the final months of the Truman administration in 1952, when the president was on a cross-country train trip campaigning for Democratic candidates, Mr. Sundquist was on board as a speechwriter.

“I remember one evening I was typing away in my compartment when I felt someone behind me and looked over my shoulder and there was the president of the United States,” Mr. Sundquist said in an oral history for the Truman Library. “He smiled at me benignly and said, ‘Don’t get up. I just wondered what stuff you’re planning to put in the President mouth tomorrow?’

“And I assumed he wanted to know and started out to tell him, but he shushed me and said, ‘That’s all right, young man, I’m sure that what you’re coming up with is going to be a lot better than anything I could suggest.’ And he strode jauntily away.”

James Lloyd Sundquist was born Oct. 16, 1915, in West Point, Utah, the son of Swedish immigrants, and he grew up on a farm near Salt Lake City. He graduated from the University of Utah in 1939, and two years later received a master’s degree in public administration from Syracuse University.

He was a top aide to Democratic National Committee Chairman Stephen A. Mitchell from 1953 to 1954, followed by two years as assistant secretary to Harriman, a Democrat. From 1957 to 1962, he was administrative assistant to Sen. Joseph S. Clark Jr. (D-Pa.) and then briefly served as deputy undersecretary of agriculture under President Lyndon B. Johnson.

Mr. Sundquist’s books included “Politics and Policy: The Eisenhower, Kennedy, and Johnson Years” (1968), “Dynamics of the Party System” (1973) and his autobiography, “Deseret Boy” (2003).

Mr. Sundquist was known as an enthusiastic tennis, bridge and cribbage player.

His first wife, the former Beth Ritchie, died in 1982 after 45 years of marriage. In 1983, he married Geraldine Coote. Besides his wife, of Arlington, survivors include three sons from his first marriage, Erik Sundquist of Arlington, Mark Sundquist of Madison, Wis., and James Sundquist of Long Island City, N.Y.; two stepsons; and three grandchildren.