Frank Capra's classic comedy-drama established James Stewart as a lead actor in one of his finest (and most archetypal) roles. The film opens as a succession of reporters shout into telephones announcing the death of Senator Samuel Foley.
Senator Joseph Paine (Claude Rains), the state's senior senator, puts in a call to Governor Hubert Happy Hopper (Guy Kibbee) reporting the news. Hopper then calls powerful media magnate Jim Taylor (Edward Arnold), who controls the state -- along with the lawmakers.
Taylor orders Hopper to appoint an interim senator to fill out Foley's term; Taylor has proposed a pork barrel bill to finance an unneeded dam at Willet Creek, so he warns Hopper he wants a senator who can't ask any questions or talk out of turn.
After having a number of his appointees rejected, at the suggestion of his children Hopper nominates local hero Jefferson Smith (James Stewart), leader of the state's Boy Rangers group. Smith is an innocent, wide-eyed idealist who quotes Jefferson and Lincoln and idolizes Paine, who had known his crusading editor father.
In Washington, after a humiliating introduction to the press corps, Smith threatens to resign, but Paine encourages him to stay and work on a bill for a national boy's camp. With the help of his cynical secretary Clarissa Sanders (Jean Arthur), Smith prepares to introduce his boy's camp bill to the Senate.
But when he proposes to build the camp on the Willets Creek site, Taylor and Paine force him to drop the measure. Smith discovers Taylor and Paine want the Willets Creek site for graft and he attempts to expose them, but Paine deflects Smith's charges by accusing Smith of stealing money from the boy rangers.
Defeated, Smith is ready to depart Washington, but Saunders, whose patriotic zeal has been renewed by Smith, exhorts him to stay and fight.
Smith returns to the Senate chamber and, while Taylor musters the media forces in his state to destroy him, Smith engages in a climactic filibuster to speak his piece: I've got a few things I want to say to this body. I tried to say them once before and I got stopped colder than a mackerel. Well, I'd like to get them said this time, sir.
And as a matter of fact, I'm not gonna leave this body until I do get them said.