Alonzo Fyfe made a great point about political positioning that I think also applies to the two party system. If you want to actually get anything done, you have to conjure up enough political backing to make it happen; it doesn't matter how right you are if nobody listens to you. You have to take the best set of positions that will still get you 51% of the vote. As a voter, you have to choose the compromise position that's more acceptable to you; voting third party leaves more power with whichever side you agree with slightly less.

Fyfe's really insightful point, I thought, was that it's incumbent upon us as citizens to create a political reality in which politicians can take the positions we all know are correct/moral/logical/win karma on /. This isn't something you do at the ballot box; it takes real work to make a substantial number of people think. The Ron Paul movement does a great job of that, but notice that he's still a registered republican.