“Lee Daniels’ The Butler” is nothing if not full of sincerity and effort. Which is why it’s so entirely confusing why they cast former teen heartthrob John Cusack as hangdog Richard Nixon. He’s fallen from his “Say Anything” days (and even the highs of “High Fidelity”), but this is maybe the worst casting we’ve seen in a major Hollywood film since Denise Richards as a nuclear physicist. Having Robin Williams play Dwight Eisenhower comes a close second, and Liev Schreiber as Lyndon B. Johnson isn’t much better. The decades-spanning drama tries so hard to create a moving, seemingly accurate look at the titular character’s time spent on the staff at the White House during turbulent times that these missteps stand out particularly strongly, especially when compared to lookalike contest winners James Marsden’s JFK and Alan Rickman’s Ronald Reagan. Casting moderately big names in these roles serves more as a distraction than anything since it’s not always a good fit of actor and historical figure. Johnson holding meetings while on the toilet may be funny, but not nearly as funny as the idea of the ancient looking president being played by the relatively youthful Schreiber. You can call us unimaginative, but we expect a little bit of realism and consistency from our overlong historical dramas, thank you very much.