I agree that Duverger's law bites. But here in the US, there are many places that are effectively one-party jurisdictions, places where one party consistently wins big. An additional party may be able to compete in such places. Thus being a party like the Parti Québécois ("Quebec Party") in Quebec, Canada.
I voted for the People's Party and the Alliance Party, because they seem the most interested in running non-Presidential candidates. The Libertarian, Green, and Constitution Party seem like borderline cases to me. They have some city councilmembers and the like, but they don't seem to have much interest in pushing non-Presidential candidates. The Unity Party, as it might be called, has shown zero interest in non-Presidential candidates so far.