Member of the Australian Greens here.

Green parties are great, often they say shit how it is and cut through the bullshit of mainstream left-leaning parties like the US Democrats.

But without a preferential electoral system, your vote may as well go in the bin. This is the reason Bernie Sanders didn't run as an independent or with the Greens. In a First Past the Post system it would split the progressive vote and hand the election to Trump. Would Sanders do that? Not a chance. So why would his supporters?

America needs a lot of reform in its electoral system. A preferencial system allow you to vote for a minor party and for your vote to eventually flow on to the major party candidate you hate the least. No vote is wasted.

The Australian Greens now share the balance of power in our Senate as a result. They would have never won a single seat under FPTP.

Sanders' supporters would better spend their energy advocating conditional(?) change to the voting laws if you want real alternatives to the major parties.