Burt Lancaster is formidable in this role. Hollywood legend has it that JFK was enthusastic about the making of this 1963 movie, even sanctioning the filming of the opening riot scene in front of the White House.
Not that Kennedy ever thought that members of the military would ever organize against the head of state. Oh wait, maybe he did. It would have been pretty hard for him to miss the fact that in August 1962, members of the French army tried to assassinate President Charles de Gaulle.
Seven Days in May is a very good movie -- but Day of the Jackal...ah, magnifique! The books from which the movies were made are also quite good.