Actually, the extremists on the other side do get to vote "FOR" someone (note the tiny vote that Nader finally got). Why? because they know that even a "centrist" Democrat will move the country incrementally in their direction.
Now limited government types like me (and I am no more "extremist" than was the 1994 GOP platform) really do "NEVER" get a vote, because a "centrist" Republican such as GWB will acquiesce in every incremental move to the left.
I am voting for my local GOP congressman who voted against CFR. I will vote third party in the Presidential election.