not sure what category but I highly recommend Street Fight about the 2002 Newark mayorial race. It may be eye opening to some to see how dirty politics can really get - for example, the incumbent uses police to harass business owners, rip down campaign signs, pays to bus in 'supporters', etc.
Given what we're part of right now, it's worth seeing the kind of stuff we'll likely be up against.
Grabbed this blurb from some movie site:
Raising hard questions about American politics, democracy and race, Marshall Curry's incisive Oscar-nominated documentary takes viewers behind the scenes of the Newark, N.J., cutthroat mayoral race in 2002. The candidates: young Ivy League upstart Cory Booker vs. incumbent Sharpe James, an old-timer who's not above employing questionable tactics to achieve victory. The gloves come off as the contenders lock horns in their battle to win voters.