"Voting for a third party accomplishes one thing. It takes votes away from one of the other major-party candidates. Given that the status quo favors the Republican candidate – think the Electoral College – voting for a third party is probably going to take votes away from Joe Biden. Whatever you think of him, he’s better than the alternative. (The alternative, by the way, likes making jokes about being a dictator.)
Actually, it accomplishes another thing. It enriches presidential candidates for third parties that do not work in cooperation with one of the major parties. (It’s called “fusion voting.”) For instance, the Green Party — these people know they can’t win. They know the status quo prevents them from winning. They don’t say that, though. In the space between what they know and what their supporters don’t know is a scam. In the absence of systemic change, third parties that don’t cooperate with one of the major parties are inherently exploitative."
Any third party presidential candidate that aligns mostly (or entirely) with one of the other parties but doesn’t join them is at best chicken shit. If you can’t convince half of the population which is closest to you politically, you’re not going to convince the other half.
The only way a third party candidate would even theoretically work is if they were moderate (think Joe Manchin) where they would appeal to moderates from both parties.
Someone like Jill Stein has no business running outside of the Democratic Party. If she can’t convince the Dems, she’s not convincing the rest of the country. Running as a Dem and convincing 26% of voters is her best road to the presidency, but she knows she’ll never get that much support.
She’s running outside the Democratic Party because she is not Democrat. That’s asking you, why don’t you vote for Republicans