Frank Langella, a decent actor, is a little embarrassing when portraying the infamous Richard Nixon. He does a caricature, and is given way too much screen time, almost to a point where he is hard to bear. He must have been having fun doing the performance, which must have been easy as hell... stuff of comedies. The rest of the movie is very well-made and does not bore for a minute.
Among the sad things of watching a movie based on actual events is the tendnecy to wonder how much of it is fiction. As for this movie, Wikipedia has a nice collection of such cases.