Director Otto Preminger offered the role of a Southern senator to Martin Luther King Jr., believing that the casting could have a positive impact (despite the fact that there were no black senators at the time). King declined after serious consideration, as he felt playing the role could cause hostility and hurt the civil rights movement.
Burgess Meredith, as Herbert Gelman, testifies against Leffingwell at the latter's confirmation hearing, claiming that the two of them were members of a Communist cell. In real life, Meredith was himself named an "unfriendly witness" by the House Un-American Activities Committee, which nearly ruined his career. Will Geer, who plays the Senate minority leader, was also blacklisted for refusing to name names before the same Committee.
Although the character of The President (played by Franchot Tone) carries no role name, at one point in the script Munson (played by Walter Pidgeon) calls him "Russ".