The Senator Was Indiscreet (1947)

Dim-witted blowhard Melvin G. Ashton is a U.S. Senator who wants to be President. He hires Lew Gibson, a talented PR man who gets Ashton in newsreels and on the front page, never thinking he'll win. But Ashton has a secret weapon: a diary documenting every shady deal his party's made for 35 years. With the diary, he blackmails the party leaders to support his candidacy, and he's on his way to the nomination. An unseen political enemy is after the diary, using the young and lovely Valerie Shepherd to get into the Senator's room. Plus, Lew's fiancee, reporter Poppy McNaughton, thinks she can get her hands on it, too, and stop Ashton. Will the otherwise unemployable dope become President?