Trump? His path to winning rests on a double down on the White non-college educated vote full pander mode and so long as he does not drive almost as many college educated White voters away in the process he can handle losing some additional Hispanic share. And it is completely possible that a few Black voters will find his demonizing another (or two) “other” as appealing. A small improvement there matters a lot. Playing with the 538 app all you have to do is get the non college educated White from 62% GOP to 69% with a 1% increase in turn out, and you can drop college educated White GOP share by 2% and the GOP wins with 273 EVs (losing the popular vote by 1%). OH, PA, FL, IA, NH, and WI flip. Still very improbable and biggest upside: the GOP puts all their eggs in the group in greatest demographic decline. Likely some major downticket wins in suburban and even exurban areas for the Democratic side.
Cruz? Similarly but perhaps not as intensely so. Not as likely to drive away college educated voters as completely.
Rubio? Likely would be just a harmful as the other two even if he plays someone less extreme in comparison. Won’t excite the White non-college educateds as much and the current GOP needs them in big numbers to win. But also won’t drive the turnout to come out against him. Clinton v Rubio would likely be a low turn out election and that helps a GOP candidate in general.