The movie that Burt Lancaster won Best Actor for, and he's a bombastic ball of energy who tears up the screen with his sleaziness in this film based on the 1927 novel. He stars as a traveling salesman who turns his talents to preaching evangelism when he stumbles across a revival meeting and immediately becomes infatuated with Jean Simmons, the lady in charge of the troupe. Lancaster's having a great time preaching hellfire to all who'll listen, a kind of early Billy Graham or Ted Haggard. It's a hugely entertaining and eerily prophetic movie that most people probably haven't seen, so you should seek it out.
Original 1960 Trailer: