My prob with docs like this **SPOILERS**
It's the manipulation of the audience by the way the stories are told. Basically this was a blowout election. The characters were quite interesting, but still: blowout election, and it's hard to believe that the filmmakers didn't know that was going to be the outcome when it was being filmed. Yet there was a clear attempt to make you think that it was going to be close--or that Dave might even win. And Dave's tumor coming back, while admittedly given a few seconds of attention well into the film, was pretty much ignored. You see much footage of energetic Dave, yet no mention of the elephant in the room: the probability that, even if he were to get elected, he wouldn't be able to do much mayoring.
I have nothing against people taking real footage and editing it to tell any story that can be coaxed from the footage. I really don't. I love those trailers like Brokeback [insert movie title here] that you see on Youtube, for example. (True, they start with fiction footage rather than nonfiction, but the fun is in the misdirection.) But when I'm trying to decide whether to watch a documentary that does that, I'd sure like some advance warning about it--a rating system or something. I'm sure that--if there are enough people on this board for this to get a response--someone's going to say that *all* documentaries do that to some extent. Perhaps, but I'm talking about degree here.
Side comment: I feel just awful about Dave. I know he was doomed in any case, but it's such a shame he couldn't have won.