We've been taught that the Democrat and the Republican are the main candidates, and maybe (depending on how much a person has believed it) the only serious candidates.
We're told that the winner of our official public elections will always be a Democrat or a Republican. And guess what: It will be, if that's always whom we vote for :-) You've heard of a self-fulfilling prophesy?
Someone once said that we shouldn't expect a different result, when we keep on doing the same thing.
So yes, keep on voting for the Democrats or Republicans if you want things to keep on staying the same.