I believe Donald Trump will join this list, primarily because until fairly recently he was a Democrat and more liberal than conservative. But even if I’m right, Trump might well scramble the GOP race, delivering major blows to “top tier” candidates and throwing lifelines to candidates not so highly rated.
Early Trump victories would thin out the field. In this context, Trump would need up to twice the support he has now to win primaries in key states like Ohio and Texas. That level of support will be extremely hard for him to obtain.