Jeff: 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.
Clarissa's letter to Jeff during the filibuster.
"Diz says I'm falling for you. P.S. He's right."
Clarissa has just called Jeff's mom to ask for help. Mrs. Smith calls her Clarissa (and not "Saunders", as most everyone does). Clarissa gives the best smile. "She called me Clarissa!" It's nice to have your future mother-in-law like you, right?
The scene at the Lincoln Memorial when Jefferson Smith overhears a little boy standing next to an elderly man (probably the boy's grandfather) and reading the "Gettysburg Address". During this, an elderly black man walks up and takes off his hat. Knowing the year the movie was made it is very possible that both men, white and black, were old enough to remember those events. Its even possible the black man may have been born a slave.