There are some options:

• grassroots voter advocacy, à la Stacey Adams
• grow and build a viable third party by joining with Democrats during electoral college cycles (or, stay at the state level until big enough)
• work with Democrats to propose, write, enact, and defend progressive policies that are wanted
• skip the politics and go into media

Those are the only other non-violent, legal things I can think of atm to change it. Obviously I think the third is most viable, but mostly that’s from watching the others not work yet. New media continues to change structures though.