Casting
Whoever was the casting director did a good job. I just saw this movie for the first time on Mojo-HD while flipping through channels and had to stay till the end. Almost everyone was believable in their roles. I could see Laughton as a dixiecrat senator from the South, Pidgeon as the Majority Leader, Murray as the freshman senator etc.
The only one off was Tone as the president. He looked more like a college professor to me.