In 1960, Duke, a personal friend of Kennedy, was asked to serve as chief of protocol for the U.S. State Department with the rank of ambassador. He held this position until 1965. As a vocal supporter of equal rights, "he resigned from the Metropolitan Club of Washington after it refused to admit black diplomats" in 1961. His most visible task during his term as chief was to supervise the protocol for world leaders who attended the November 25, 1963 funeral of John F. Kennedy.