"Though most people commonly think of parties as national organizations, nearly all party building happens at the state and local levels. ...
Third parties succeed when people get elected under that party's banner or the party's candidate gets enough votes to affect the larger political debate and change people's political awareness. A third, more subjective measure of success is when a third party shows that it is not a flash-in-the-pan phenomenon but actually builds an enduring organization that is self-supporting and growing. ...
The idea of "bearing witness" against a corrupt and seemingly impenetrable political system can be noble. But it is usually not very political in the sense of actually affecting the direction of the country. That requires a willingness to engage in dialogue with real voters, not just true believers, no matter how hard that may be. So one critical element of third-party growth is whether the party's activists are outward focused (on winning elections or moving issues) or inward focused (on often irrelevant organizational or ideological battles). ..."
- From Spoiling for a Fight
This seems to point at the tough work of building a real base is the key work. Registering voters, developing volunteers, donors, and leaders. In essence we need activists - volunteer at first and eventually paid - who do the nuts-and-bolts of building the party, supporting candidates, and getting the word out.
Lots of working-class and poor people know that the current set up isn't helpful to them. They are blown off as apathetic, but knowing you are locked out is not apathy. So what to do?
Build options! Large numbers of people are interested in alternatives. Many people support aid to poor families, eliminating corporate welfare, reductions in military spending, universal health care, poison free communities, better labor conditions, healthy energy systems, healthy food, and many more progressive issues that come down to working people having real power.
So get out there and register someone!