It's self selecting. You speak out against trump/Maga and a further right candidate primaries you and may win. Or you get so sick of associating with trump/Maga you quit because you know the primary with put you out.
I don't understand why Democrats keep doing stuff like that. Nobody's going to change their mind because some never Trumper says so. I guess this is a slight improvement over having the guy that poisoned Flint 4 years ago (who coincidentally never got charged because the investigation got messed up).
There were anti Trump republicans, some even voted to impeach him, but they've all been purged or are in the process of being purged. Because now the Republican party isn't about an ideology as much as it is a messianic cult around Trump.