Sen. Jefferson Smith
Jefferson Smith is the head of the Boy Rangers, beloved by many young boys in his home state. Hopper chooses him to join the Senate because of his naiveté and pleasant image. When he arrives in Washington, he seems like a bumpkin, overwhelmed by the big city ways and the sophistication of politics, finding that the system is not nearly as idealistic and majestic as he expected. While his simple and straightforward love for country seems like a handicap at first, it eventually becomes the artillery that he wields against the corrupt ways of his superiors, Paine and Taylor. Smith's disappointment in the cynicism of Washington becomes the thing that drives him to fight back against injustice and stand up for what he believes in. Smith might seem like a hapless nobody, but his deep love for America, his resilience, and his sense that he can make a better world strengthen him and allow him to change policy for the better in Washington.
Senator Paine
Senator Paine takes Jefferson Smith under his wing, and acts as if he wants to help him, even though he secretly hopes for his failure. He works under Taylor, a bullying brutish hood who controls the political system in his state. Paine is beloved in his state, in part because Taylor helps to amplify Paine's image in the press. Paine also knew Smith's father, and admired his idealism, a trait his son shares. Throughout, he is haunted by the memory of Smith's father and his lasting belief that "Lost causes are the only causes worth fighting for." Paine has sold out and compromised his ideals in order to have a career in Washington, but he eventually cannot take the pressure of that corruption anymore, and chooses to reveal the truth to help Jefferson Smith's cause.
Clarissa Saunders
Clarissa Saunders is Senator Paine’s secretary, a cynical, savvy, and fiercely smart young woman who is fed up with the corruption of politics, but also wants to influence it in whatever way she can. She knows Washington and its political ins and outs, and uses this knowledge to help Smith gain power in Washington and speak truth to power. In the process of helping Smith, Saunders falls in love with him, taken in by his dream of a better America and his charming earnest attitude.
Jim Taylor
Jim Taylor is the political "boss" of Paine and the other politicians in Jefferson Smith's home state. While he spins it to look like he is working for the common good, he is nothing more than a common crook, working only for his own profit and power. He is an unsavory villain, who bulldozes people into doing what he says with no thought of how it affects the moral fiber of his community.
Diz Moore
Diz Moore is a journalist in Washington and a close friend and confidante to Saunders. He is a hard-drinking Irishman, who can more often be found at the bar than at his typewriter, but when he does write, he writes on behalf of goodness and the truth. He has a crush on Saunders, and hopes that one day she will cave and marry him, but eventually realizes (and is the one to point out) that her heart is Smith's.