are you a 'choose the lesser of evils' voter?
then you are a supporter of the greater evil.
first, by participating in the election process, you legitimize the winner. your vote for either or any candidate is implicit acceptance that whoever gets the most votes should rule america. doesn't matter what kind of murderous creep he turns out to be, you made it possible for the murderous creep to say, "hey, you voted..."
worse than that, by accepting your role as a 'captive lefty,' you make it possible and desirable for the democrat party to seek votes on the right, since the votes on the left are sewn up. this is why the democrats have been drifting left for the last 40 years- you made it possible. why has the republican party been able to get away with blatantly esposing right wing nonsense? because the democrats are following them to the right, in search of votes they don't have 'sewn up.' so when you read some 'progressive's' complaint about obama being a closet republican, laugh at him. it's his own fault.
if you want to do something about it, i wrote a brief sketch of (nonviolent) revolution in my post called: 'revolution, and democracy' , or come up with a better plan.
one thing though, the only way you can be sure you are wrong, sure you are part of the problem, is to go on voting for politicians.