I feel this is one of the best documentaries of all times. It takes a ridiculously complex system (that being America's electoral process) and gives the viewer a great idea of how it all works in less than two hours.
In Street Fight you get to see the full process warts and all. You get a great "villain" (the incumbent Newark mayor Sharpe James) and a great, shining hero (upstart opponent Cory Booker) and you get to see all the convoluted machinations and strategies each side uses to get out/keep in the vote. It is, of course, biased towards one side but that's how elections are.
In a perfect world, it would be required viewing for high school social studies students that are preparing to vote for the first time.