Macdonald attended Harvard University, where he was captain of the football team and the roommate of John F. Kennedy.
After several years in public school, he entered Phillips Academy in Andover. They remained close friends throughout their lives, with Macdonald serving as an usher at then-Senator Kennedy"s wedding and as an honorary pallbearer at President Kennedy"s funeral. At Harvard, Macdonald earned his Bachelor of Arts in 1940 and his Bachelor of Laws in 1946 from its law school.
Macdonald was elected as a Democrat to the Eighty-fourth Congress in 1954.
During his career, he served as Majority Whip, and as ranking Democrat on the House Committee on Interstate and Foreign Commerce. He was often referred to as the "Father of Public Broadcasting", since he was one of the legislators primarily responsible for Public Broadcasting Acting of 1967.
He was also responsible for the "sports blackout bill" which provides for the broadcast of local sold -out sporting contests. Another focus was his effort to reform campaign broadcasting practices, addressing his concern that competent candidates were being priced out of the process, and others were buying their way in.
While recognized as an active legislator, he was also justly noted for his high level of service to individual constituents and their problems.
His sharp wit and sense of humor garnered him among his Congressional colleagues the nickname "The Needle". He was reelected ten times, and died in office on May 21, 1976, in Bethesda, Maryland. They had four children, the eldest of whom was President Kennedy"s godson.
Macdonald was interred in Holy Cross Cemetery in Malden, Massachusetts.
He served as a Democratic member of the United States House of Representatives serving from 1955 until his death from internal hemorrhage in Bethesda, Maryland in 1976. Macdonald was a member of the National Labor Relations Board for the New England area from 1948 to 1952, and he was a delegate to the Democratic National Conventions in 1960, 1964, and 1968.
Married Phyllis Brooks, June 1944. Children: Torbert Hart, Laurie, Brian, Robin.