Because of the extensive parody of Katherine Harris in the media, Laura Dern expressed great apprehension over how to approach the character. Dern convinced director Jay Roach to allow her at least three takes for every scene: one underplayed, one "medium," and one way over-the-top, so Roach could help guide her performance.
Danny Strong made it his goal to interview the real-life counterpart of at least one character appearing in each scene. In most cases, he actually ended up interviewing every character. He achieved his goal in all but one case: because Katherine Harris declined any interviews, the scene where she stands alone looking out over the crowd of protesters outside her office was entirely imagined.
Most of the cast met with their real-life counterparts prior to filming. The real Katherine Harris refused to meet with Laura Dern or anybody else associated with the production, despite repeated pleas from Dern, writer Danny Strong and director Jay Roach.