Consider Robin Hood and his Merrie Men - no matter how that shook out, they ended up subject to a f*cking King. Do you really think there was more difference between Richard and John than between Russ Feingold and Ron Johnson?
You can either play the game on the field, choosing between unworthy candidates, or vote for somebody you really believe in, who isn't really in play. But who am I to try to stop you scoring a touchdown in this baseball game?
The game on the field is one where it is far more likely that you are picking the less repugnant of a distasteful pair than backing your hero. Considering the track record of heroes as seen from the point of view of a guy who will be played by an extra if they ever make a movie, I think that's a good thing, well worth the angst of voting for some unworthy clod.
Your odds of getting your sorry ass to your crappy job in one piece tomorrow morning are considerably better if you are barely tolerating a politician than if you are being led to glory by a hero.