I remember quite a bit from my History and Civics classes. Of course, admittedly, my brain is a sponge for useless facts. Well, I enjoyed History, and did find it important to know how the government works. Although, I used to be able to count to 100 in French, and now I can only count to 39. I guess it depends on what interests you, and how much you use it.
I do think voters should be better informed, but of course, you can't force people to learn. The public school system has been trying to do that for a very long time, and it hasn't worked so far. I only had to pass the national standardized test for Reading and Math to graduate.
But I still don't think it would be a horrible thing to make candidates prove they have some grasp on how it all works. They are the ones that have to run everything after all. There are probably Congressman who couldn't pass the citizenship test. If you just use that test, then at least you would weed out those who don't have a grasp on reality.