HBO’s “Game Change” was a critical darling this year, securing Emmys for the movie and actress Julianne Moore. And now, the network is looking for a follow up. “Double Down: Game Change 2012” will be based on a book currently in the works by Mark Halperin and John Heilemann, the team behind the book on which the first film was based. The sequel will document the reelection of President Obama over Mitt Romney.