The HBO film, written by Danny Strong, will be directed by Jay Roach and follows John McCain's (Harris) 2008 presidential campaign, from his selection of Alaska Governor Sarah Palin (Moore) as his running mate to their defeat in the general election.
Paulson has signed on to play McCain's senior campaign advisor, Nicolle Wallace. MacNicol will play McCain's campaign manager, Rick Davis, and Harrelson is set to play Steve Schmidt, McCain's senior campaign strategist and advisor.
Harris received a Tony nomination for his performance in Precious Sons and has also been seen on Broadway in Taking Sides. Moore has been on Broadway in The Vertical Hour and her children's book, "Freckleface Strawberry," inspired the Off-Broadway musical of the same name that will resume performances Aug. 3 at the new MMAC Theatre.
Paulson's credits include Collected Stories and The Glass Menagerie. MacNicol has been seen in White Liars & Black Comedy, The Nerd and Crimes of the Heart, and Harrelson has appeared in The Rainmaker and Biloxi Blues.
"Game Change" will be produced by Tom Hanks and Gary Goetzman's Playtone. An air date for the film has not yet been set.