"If I vote for a democrat I am going to get a liberal vote in the congress. If I vote for a republican, I am going to get a liberal vote in the congress. If I vote libertarian, I may get a democrat or a republican in the congress and I still get a liberal vote in the congress"
No, if you vote Libertarian you get no vote in the congress since they don't win.
Either way, democrat, republican, libertarian or no vote, we still get a liberal vote in congress.