Yet, people are always saying we only have 2 choices and don't talking about "wasting my vote". If enough people voted 3rd party, it would no longer be a "3rd party".
It has happened once when the Republican Party supplanted the Whig party, right before the civil war; but I doubt that could happen again with the "advances" of media, polling, and propaganda (and if Trump wins, I doubt the U.S. will have fair elections again). There's no other "big tent" party like the Democratic party; so a left-leaning third party could only just siphon off a fraction of the votes from the Democratic Party, ensuring Republican victory. We have two-party rule because when people act rationally in FPTP electoral systems, that's what happens (https://en.wikipedia.org/wiki/Duverger's_law).
Though, I'd argue that MAGA supplanted the Republican party from within. That seems like the most viable option for progressives (supplanting the Democratic party from within).