Libertarians have been the principled alternative to Left and Right ever since 1971, when David Nolan published his article called “Classifying and Analyzing Politico-Economic Systems” in The Individualist, the monthly magazine of the Society for Individual Liberty.
I’m curious how Greens see themselves as distinct from the Left; decentralized socialism is still socialism. When I plug the platform positions of the Greens and the Democrats into my 20-question test at http://marketliberal.org/test/, both fall into the same neighborhood on the Left side of the chart. I’m doubt any Green can come up with 20 questions that would accurately plot the Dems as Left and the GOP as Right but the LP and the GP as neither.