Hence my original point, leftists must vote for liberals, even if it isn't ever going to improve the system, and must work themselves to build up leftist structures without hoping for help from liberals. If they don't vote, then fascists take power, and leftists lose the chance to build leftist structures at all.

I do think you're too hopeful that a 2 party Capitalist state designed to change as little as possible would meaningfully improve from within, rather than under pressure from without, but it would be great if you were right about that.