The big problem is that the First Past The Post system always devolves into 2 parties. Let's say a Progressive Party launched tomorrow and got 25% of the left leaning votes. Some of those people would be folks who didn't vote before, but many would be Democrats who feel this party represents them better.

This isn't a bad thing in and of itself. People should be able to vote for parties that represent them the best. I'd be upset if my only ballot choices were "Classic Republican" or "MAGA" because neither would represent my views.

However, remember that many of the hypothetical Progressive party's voters would come from Democrat voter rolls. This would mean that Democrat support would drop. Again, not a bad thing but itself. Keep up with the times or get left behind.

The problem comes when the Democrats drop so low that Republicans start winning elections due to the Progressives pulling votes away. Maybe this is all temporary and would eventually right itself when the Progressive Party becomes the dominant party. Still, there would be a stretch of time when Republicans would rule nearly uncontested.

Just looking at Congress, imagine a Congress that was 70% Republican, 15% Democrat, and 15% Progressive. Items like a national abortion ban, banning any mention of LGBTQ, shooting illegal immigrants on sight, and arresting liberals for speaking up would have a shot at passing and wouldn't be able to be stopped. Even if the situation righted itself eventually and the Progressive Party took control by enough to enact their agenda, they'd have a massive mess to clean up.

That's why we need Ranked Choice Voting or Approval Voting first. It would let third parties grow without taking votes from the closely aligned major party.

if they didn’t hit the threshold in 2020 they’ll never hit it. If they had any desire to actually govern they would have put more effort into their candidates too. Jill Stein was less qualified to be President than Trump, and that’s saying a lot. She literally wasn’t qualified enough to run a medium size organization. It was a complete joke how she went around and agreed with every crackpot far-left conspiracy theory in her town halls because she couldn’t risk either upsetting any voter or possibly crossing her questionable Russian backing. Not saying she was a Russian plant, I think she was much more a useful idiot than anything. Gary Johnson didn’t know so many basic facts that he should have known it was clear he just ran to keep his name out there. We see this time and time again. Nader was the last genuine one to run and even he figured out he was accomplishing the opposite of what he wanted to eventually.

Plenty of representatives in Congress right now are there because of grassroots campaigns. Third-party candidates could get elected without major backing, but they for some reason act like it's impossible. And that's the problem with third-party supporters: you all want all the clout and recognition of the major parties, without decades of putting in the footwork to get there. Just saying "We're here! Vote for us!" isn't gonna cut it.

When a third party creates a platform with clearly-defined policies and objectives, ideas on how to accomplish those objectives, and puts in effort to win local and state elections, then they'd be considered a viable alternative. But when a party only pops up every four years and whinges about being taken seriously... it's obvious they're nothing but a spoiler.