A voting machine malfunction in a small town in New Mexico results in Bud Johnson's (Kevin Costner) ballot not being counted. Because the Presidential race is so close, his vote will decide who gets the state's electoral college votes and becomes the next President. Knowing that one man will decide the election, both candidates fly to the state and try to influence Bud, who becomes the center of a media circus. What no one knows is that Bud's civic-minded daughter Molly actually sneaked into the polling center and cast the ballot herself while Bud was passed out in his truck.
After Bud disappoints her yet again, Molly goes to the house of Kate (the reporter) to tell her the truth about what happened on election day. Just as she's getting ready to reveal everything, Molly notices that Kate has set up a video camera and is secretly taping the confidential talk. She runs away and finds her friend Jed, who promises to drive her to her mother's place in Albuquerque. Meanwhile, Molly's disappearance makes Bud realize just how little he knows about his daughter and how much he has let her down. When she arrives in Albuquerque, Molly finds that her mother is a drug addict who doesn't want anything to do with her. Bud shows up, argues with Molly's mom, then takes Molly home.
Once Bud and Molly get back to their trailer, Kate meets them and subtly indicates that she knows what happened at the polling center but is not going to tell anyone. After she apologizes and gives Molly the tape of their conversation, Molly asks her to help Bud prepare for the Presidential debate. Molly, Kate and Bud's bodyguard spend the night teaching Bud about the issues.
On the night of the debate, Bud begins the event by reading a very emotional statement in which he admits that he has wasted the opportunities that he had. He says that he didn't do his part in the political process and that people like him are the real enemies of democracy. He then begins to read his questions, all of which come from the thousands of letters that people sent to him. The next day, police guard the entrance to the polling center as Bud drives his truck through a circle of newsvans. Once inside, Molly beams with pride as she watches her father go into the voting booth to finally cast his ballot.
(The movie fades to black without ever indicating who Bud decided to vote for.)