In “Martin Luther King,” Dr. Harding argued that in focusing toward the end of his life on social imperatives like eradicating war and poverty, Dr. King was more radical than many Americans feel secure in acknowledging.

“Men do not get assassinated for wanting children of different colors to hold hands on a mountainside,” Dr. Harding said in a 2005 lecture. “He was telling us to march on segregated housing, segregated schools, poverty, a military with more support than social programs. That’s where he was in 1965. If we let him go where he was going, then he becomes a challenge, not a comfort.”

Vincent Gordon Harding was born in Harlem on July 25, 1931, and reared by his mother, Mabel Lydia Broome, who worked as a domestic. They moved to the Bronx when Vincent was a youth, and after graduating from Morris High School there, he received a bachelor’s degree in history from the City College of New York and a master’s in journalism from Columbia.

After Army service — an experience, he said, that made him a committed pacifist — he earned a master’s in history from the University of Chicago, followed by a Ph.D. in history there, writing his dissertation on Lyman Beecher, the Protestant minister, antislavery advocate and father of Henry Ward Beecher and Harriet Beecher Stowe.

In Chicago, Dr. Harding also served as a lay pastor in the Mennonite Church. In the late 1950s, as a church representative, he traveled to the South to observe race relations there. On that trip, he met Dr. King and became deeply influenced by him.

In the early ’60s, Dr. Harding and his wife, the former Rosemarie Freeney, moved to Atlanta, where they established Mennonite House, an integrated community center. The site they secured for it happened to be the childhood home of the soprano Mattiwilda Dobbs, among the first black singers to perform with the Metropolitan Opera.

In Atlanta, Dr. Harding joined the department of history and sociology at Spelman College, becoming the department chairman. At the same time, he contributed speeches for Dr. King.