The third time that Michael Sheen plays former Prime Minister Tony Blair. The other two movies in which he earlier appeared as Blair were The Queen (2006) and The Deal (2003).
Hope Davis replaced Julianne Moore as Hillary Clinton. Moore, who had been the first choice, but withdrew from the production.
With the look of the real characters in place, dialogue coach Penny Dyer had to make sure the actors had the authentic voices of the people they were portraying. Dyer explained: "We never attempt to do an impersonation, because that is something that comedians do. Actors inhabit the characters, and my job is to bring the anchor qualities that will help create the reality of that person. It's not just about vowels and consonants. It's really about helping them find the physicality, the vocal quality and the energy that informs their character."
Mark Bazeley reprises his role from The Queen (2006) where he portrays Tony Blair's aide Alastair Campbell in both movies.