Season four follows the re-election of President Bartlet to his second term and we witness the gripping personal crisis that forces him to chose between the best interests of the country and those of his family.

After nearly eight years, President Bartlet's time in the White House has come to an end, and two formidable men vie for the Presidency: Arnold Vinick, a Republican senator from California, and Matthew Santos, a three-term Houston Democratic congressman. After suffering a heart attack, former Advisor to the President Leo McGarry resolutely serves as Santos' vice presidential running mate, ably assisted by Annabeth Schott. Former Deputy Chief of Staff Josh Lyman keeps his highly regarded political mind in overdrive as Santos' campaign manager.