The Little Man Against the System
Frank Capra’s overarching thematic concern, one which extends across several of his films, is the theme of one individual going against the system to improve the world. Every aspect of political life conspires to beat the little man down, first as represented by the greedy and malevolent Jim Taylor and then as represented in the Washington establishment types who laugh off Smith's highest ideals. Much of the film's drama as well as its thematic tension is based around a single character's attempt to buck this system—to save democracy by reasserting the power of a single individual.
Jefferson Smith is defined by his small-town appeal and the fact that he is a bit of bumpkin, unfamiliar with the sophisticated and fast-paced ways of society. He struggles to keep up with the world around him, but his insistence on his own personal beliefs keeps him showing up in the Senate and working hard to fight for what he believes in, in order to take on corruption.
Cynicism
Another theme the films explores is the way that cynical beliefs can spread and affect an entire system. The body politic into which Mr. Smith steps is headed by business interests, swayed by a cynical and opportunistic approach to capitalism that prevents individuals and organizations from working for the common good. The cynicism of politics is typified by Senator Paine, who once held lofty ideals, but caves to pressures from manipulative bad guys like Jim Taylor, and compromises his beliefs in favor of keeping his career. At one point, Paine tries to discourage Smith from going up against Taylor, telling him that part of becoming a man is making compromises and giving up on naive dreams. This cynicism is emblematic of a broader attitude in Washington.
Conspiracy Theory
In a way, Mr. Smith Goes to Washington is one of the first Hollywood movies to foster the conspiracy that the country is actually being run not by the politicians elected to office, but a tiny secret cabal of powerfully influential business interests. By the time the film was made, the power of these machines had waned considerably from their heyday around the turn of the century. But the idea that powerful political conspiracies controlled the country became increasingly prevalent over the course of the 20th century, and Mr. Smith marks one of the earlier instances of a new genre of "conspiracy" films that—after World War II especially—would become a staple of Hollywood.
Lost Causes
At one point, Jefferson Smith alludes to one of his father's central beliefs: "Lost causes are the only causes worth fighting for." Smith's father was murdered when he was working as a journalist trying to expose greed in his town, speaking truth to power and fighting for what was right. It is this belief, that one must always stand up and fight for important causes, even if they are unpopular or do not have widespread support, that keeps Smith going.
At the end of the filibuster, Smith says, "I guess this is just another lost cause, Mr. Paine. All you people don't know about lost causes. Mr. Paine does. He said once they were the only causes worth fighting for, and he fought for them once, for the only reason any man ever fights for them: Because of one plain simple rule: Love thy neighbor. And in this world today, full of hatred, a man who knows that one rule has a great trust. You know that rule, Mr. Paine. And I loved you for it just as my father did, and you know that you fight for the lost causes harder than for any others." Lost causes are an important part of Smith's sense of what is right and his purpose in the world.
Nature
Another guiding principle in Smith's life is his love of nature. In fact, Saunders and Moore call him "Daniel Boone" before they have even met him, as a kind of sarcastic homage to his Western upbringing, his love of the frontier, and his status as the head of the Boy Rangers.
When he and Saunders sit down to write the bill for a boys' camp, he goes into an expressive monologue about his love of the American West and his appreciation of its natural beauty, describing it with such affection that the cynical Clarissa Saunders gets a tear in her eye at the thought.
Patriotism
Even though Smith does not know all the secret rules of Washington politics, he has a fierce patriotism that guides him at every turn and which anchors his desire to do the right thing. He is a true American history wonk, and when he first arrives in Washington, he marvels at all the landmarks that define the city, including the Capitol Dome and the Lincoln Memorial. While his peers do not care as much about the history of Washington, and are instead caught up in ambition and ascending the ranks in politics, Smith has a pure love for his country and its ideals that guides his every move.
Boyhood and Adulthood
When Paine tries to "talk some sense" into Smith, he tells the young newbie that in order to "become a man" Smith has to cede to the standards of Washington, however crooked they may be. He makes a distinction between being a boy and being a man, suggesting that boys have ideals, while men compromise them in order to have careers.
Smith represents someone who refuses to transition into manhood in the way that Paine describes it. His commitment to his ideals is his commitment to his own youthful sense of possibility, and he is determined to remain a boy for as long as he can, and to give other boys the opportunities to cultivate their senses of self at a boys' camp. At the end of his filibuster he says, "I wouldn't be a bit surprised if some of these Senators were boys once. And that's why it seemed like a pretty good idea for me to get boys out of crowded cities and stuffy basements for a couple of months out of the year. And build their bodies and minds for a man-sized job, because those boys are gonna be behind these desks some of these days. And it seemed like a pretty good idea, getting boys from all over the country, boys of all nationalities and ways of living."
