Where I live we get lots of local candidates who are some combination of democrat-green-progressive-working family alliances. Building coalitions from the bottom up like that, and showing that people with “green” in their bio can really be elected, is the way to move things forward. At the national level, the two-party system is far too entrenched to have a third party be anything but a defacto spoiler that turns off their own supporters more that anything else.