Born in Massachusetts in 1943, Gable graduated from Lenox School for Boys in 1961 and Kenyon College in 1965. He received a Ph.D. in History from Brown University in 1972. Thereafter he held adjunct positions in the history departments of C.W. Post/Long Island University, Briarcliff College, Brown University, and Hofstra University. Gable's publications include The Bull Moose Years: Theodore Roosevelt and the Progressive Party (Port Washington, NY: Kennikat Press, 1978). In 1975 he founded the quarterly Theodore Roosevelt Association Journal. Gable served as consultant and on-screen commentator for numerous television productions concerning Theodore Roosevelt. He also served on the vestry of Christ Church (Oyster Bay), was a past-trustee of the Oyster Bay Historical Society, held a seat on the Theodore Roosevelt Memorial Committee at the American Museum of Natural History, and was a member of the Advisory Board for the Roosevelt Study Center in The Netherlands. Shortly before his death, Gable was awarded the Theodore Roosevelt Association's Distinguished Service Medal, an honor previously granted to David McCullough, George H.W. Bush, Helen Keller, Paul Nitze, Philip Habib, Ralph Bunche, and Robert Frost.