The Best Man (1964)

Secretary of State William Russell (Henry Fonda) lives by his principles, but is haunted by a recent sexual indiscretion that threatens both his marriage and his career. Senator Joe Cantwell (Cliff Robertson) presents himself as the people's candidate, yet his determination to win at all costs is also his great flaw. These two frontrunners for their party's presidential nomination vie for the support of the outgoing president (Lee Tracy), and resort to mudslinging in a very public contest.