Looking back over the history of how Hollywood has always portrayed authority and power, it's easy to see how radical this movie would have been. Nowadays you can be sure than almost any powerful figure in a movie from a congressman to the CEO of a gigantic company will turn out to be the main villain behind the scenes because it reflects the social mores of today. We reflexively don't trust governments, big corporations or those in power, immediately attributing self-interest, greed and corruption to them.

But Mr Smith Goes To Washington was made at a time when people believed anything they heard on TV, respect for political power and your elders was deeply entrenched and ruling institutions like government or church were above question or criticism. I'm not sure, but it might have been one of the first stories about the corruption in government's collusion with big business. That's especially true on the eve of the Second World War when Americans would be rallying behind their elected officials to save them from marauding and bloodthirsty Japs.

Director Frank Capra lays out his playing field from the opening frames. After the sudden death of a state senator, the governor is trying to decide between two replacement candidates, and the fact that he's consulting with powerful local businessman Taylor (Edward Arnold) to select a candidate that will align with Taylor's interests is quite up front.

But Taylor's power isn't absolute and the job instead goes to scout leader and beloved local figure Jefferson Smith (James Stewart at his most lovingly shambling). Smith is naive, idealistic and believes wholeheartedly in the sanctity of the institution he's entering. He no sooner stumbles off the bus in DC than he walks off alone, visiting the landmarks of US politics in awe the way an LA tourist traipses, wide eyed, between Disneyland, Hollywood Blvd and Venice Beach.

Nevertheless, he's there under the strict understanding behind the scenes that he'll be controllable and not rock the boat. The senior senator from Smith's home state, Paine (Claude Rains) is Taylor's proxy to ensure Smith's bumbling persona doesn't develop into anything too dangerous – like actually doing his job.

But while Smith's naivete is a potential liability to be kept in check to Taylor and Paine, it's a beacon in the dark cynicism of DC machinations to the knowing secretary at his office, Saunders (Jean Arthur), who's drawn to his innocence and cluelessness despite her battle-hardened exterior.

Even along with Smith's getting under her skin and seeming like the active participant in their relationship, Saunders might be the another great portrayal of a woman from Hollywood's golden age alongside Rosalind Russell in His Girl Friday – whip-smart, fast-talking and still very human, she holds her own against the men around her in an age where women were hardly welcome in politics at all.

However, she knows the system is going to chew Jeff up and spit him out, and it isn't long before he comes up against the way Washington truly works. Paine suggests Jeff start working on a bill of his own to get some experience (and keep him out of the way), and the latter just happens to hit upon an idea to have the government buy wilderness back home to set up boy's scout camps.

The problem is, it's the same tract of land Taylor wants for his dam, and Smith already has a head of steam behind him. When Paine tells him to drop it Smith is confused and hurt but stands his ground, setting the stage for the grandstanding climax of the movie.

Desperate to rid themselves of the new thorn in their side, Paine's overseers orchestrate a smear campaign against Smith, but he's still sure he has the support of his people. Desperate, they instruct Paine that they want Smith gone, and Paine formally dismisses Smith from his seat. But becaue of the laws of the chamber, Smith is allowed to use the current session to state his case. He holds the floor for a full day and night, exhausted and ready to drop, while Saunders and others try to rally supporters from his fans back home, and it's an effective way of producing a powerful Hollywood moment with some of the outlandish strictures of institutional political work.

The only slight niggle I had was that even though it's Smith who digs his heels in and is therefore the heroic figure, the final act that seals his fate comes from a character who's been far less active until then. It made it feel a little bit like Smith didn't really do anything, he just stood still while someone else came in to rescue him.

Capra (working from a script by Sidney Buchman) revists the theme that would make It's a Wonderful Life a smash years later – of the little guy speaking truth to power and stopping a corrupt juggernaut in its tracks by simply not giving in. He even revisited Stewart's likeability by using him again (and has the same actress, Beulah Bondi, play Stewart's mother in both films).

It's wish fulfilment executed with comic panache and a script that treats ballsy wisecracks just as seriously as impressionable idealism.