PBS has updated and is rereleasing this 1996 documentary about third parties and how they effect US politics. I strongly suggest watching it: especially if you want to see change.
Change does not come from the duopoly, change is forced on the duopoly from the outside.
From the transcript:
When Americans demand a third choice, or even a fourth choice, it can change and renew the major parties, sometimes making winners into losers and vice versa.
More often than you might think, Americans have looked beyond the two major political parties and reached for a third choice. When they do, big things often happen in American politics and in American life.
Let's start at the beginning. First, why two parties? In fact, why parties at all?
In the beginning, the founders agreed they wanted no parties in their new country.
"There is nothing I dread so much as the division of the Republic into two great parties, each under its leader" - John Adams.
"Ignorance leads men into a party, and shame keeps them from getting out again" - Benjamin Franklin
"If I could not go to heaven but with a party, I would not go there at all" - Thomas Jefferson.
Vote for the duopoly candidates only if you are satisfied with the current situation.