Swing Vote (2008)
Swing Vote is a 2008 comedy-drama film about an entire U.S. presidential election determined by the vote of one man. It was directed by Joshua Michael Stern and starred Kevin Costner, Paula Patton, Kelsey Grammer, Dennis Hopper, Nathan Lane, Stanley Tucci, George Lopez and Madeline Carroll. The film was released on August 1, 2008.
More at Wikipedia.