season three seemed to have been the "set up" season for a ramped up political FIGHT that is goign to be intriguing. All the new chess pieces are put into place with enough backround for us to keep up with. There actually was a LOT of things that happened in 3, and a lot of new players.
(like wave pointed out, when Frank went to college and was kissing on his college friend was the first time we were introduced to his bi side. We just didn't know if his wife knew until the SS agent)