Seven Days in May - John Frankenheimer

An unpopular U.S. President manages to get a nuclear disarmament treaty through the Senate, but finds that the nation is turning against him. Jiggs Casey, a Marine Colonel, finds evidence that General Scott, the wildly popular head of the Joint Chiefs and certain Presidential Candidate in 2 years is not planning to wait. Casey goes to the president with the information and a web of intrigue begins with each side unsure of who can be trusted.