first past the post system is responsible for a lot of this. It is impossible for a third party candidate to enter the ring as they would just ruin the chances of the next closest candidate to their ideas, guaranteeing a worse candidate getting in. Americans cant vote out the republicans, they exist to give the illusion that there is an alternative to communism but they are just as bad. This polarity is inevitable because nobody votes for who they actually think is good, they just vote to oppose who they know is the worst. Though i suppose it doesnt matter when different forms of government have all being subverted too through cheating.