For a second I thought this was the Mel Gibson movie where he proves a Conspiracy Theory (1997)... but Gene Hackman, post-Watergate — with an ensemble cast of eavesdroppers?! — tonight's movie, decided.
Thank you for your recommendation - it be crazy up in here (head, country, world).
Directed by Francis Ford Coppola, Palme d'Or at Cannes, three Oscar nominations including Best Picture (which, amusingly, it lost to The Godfather Part II).
Great movie.
One fan theory is that Gene Hackman plays the same character, decades later, in Enemy of the State (1998).