Born in Mississippi in 1924, Campbell suffered a near fatal case of childhood pneumonia. After recovering, Campbell felt that he had been delivered by providence, and was destined for the ministry. He was ordained at age seventeen before attending Louisiana College and serving in the South Pacific during World War II. Campbell went on to study at Wake Forest, Tulane and Yale, after which he briefly pastored a Baptist church in Taylor, Louisiana. He quickly learned that the life of a small town minister was not for him, and attempted a career in academia, thinking a university would offer him more freedom than church, which he insists "is a verb, not a noun." He served as director of religious life at the University of Mississippi from 1954 to 1956, during which time he felt stifled by a similar degree of institutional pressure. His relationship with a group of missionaries who provided medical treatment to the needy, regardless of race, was controversial at the University, as were similar activities of his.
Campbell left the University to serve as Executive Director of the National Council of Churches' Summer Project operating out of Nashville, Tennessee. There, Campbell kept a low profile while participating in a variety of civil rights conferences and direct actions. When nine black students planned to integrate Little Rock's Central High School, Campbell was among four adults who accompanied them on their first attempt, upon which they were turned away. In 1962, Campbell once again felt stifled by the organization he was a part of and left the National Council of Churches to join the Committee for Southern Churchmen. Campbell has always had more of a passion for spreading a gospel of reconciliation than for aggressive public activism. He currently lives with his wife Brenda on a farm in rural Tennessee where they have raised three children. He has written seventeen books and continues to lecture and preach his version of "first-century" style Christianity.