A third party helps X in which X is the candidate you hate the most. This is a common line that is regurgitated over and over and over and over and over and over and over and over and over and over and over and over and over again. And over and over and over and over and over and over and over again.

If you want Trump to win, vote for Trump. If you want Biden to win, vote for Biden. If you don't want either to win, vote third party and use your own vote in a way you want to not the way others want you to. That is what I wrote.