By Dan Snierson
Updated September 10, 2011 at 12:00 PM EDT

Cliff Robertson, who portrayed John F. Kennedy in P.T. 109 and later won an Academy Award for his role as a mentally disabled man in Charly, died Saturday of natural causes, according to the Associated Press. He had turned 88 one day earlier.

The film, television, and theater veteran enjoyed a career that spanned more than five decades, making his big-screen debut in the 1955 romantic drama Picnic opposite William Holden and Kim Novak. He would appear in dozens of films, including The Girl Most Likely, Gidget, Sunday in New York, The Naked and The Dead, The Devil’s Brigade, Three Days of the Condor, and more recently, the Spider-Man movies as Uncle Ben Parker.

A popular leading man in the ’60s, he played a sitting President — John F. Kennedy — in the 1963 World War II-set drama P.T. 109, after Kennedy gave his casting approval. Five years later, he scored an Oscar for his touching portrayal of mentally challenged bakery employee Charlie Gordon in Charly, which was based on the novel Flowers for Algernon. Robertson — who won an Emmy in 1966 for his performance in an episode of Bob Hope Presents The Chrysler Theatre — also appeared in such TV series as The Twilight Zone, Batman, and Falcon Crest, and in commercials for AT&T. He earned attention as well for blowing the whistle on a film studio president who had victimized him in a check forgery scheme in 1977.