 In alternative history, if one of those, whether Rubio, Bush, or Cruz, if the party coalesced around one of them, they might have won the nomination, and Trump would have just gone back to being a reality television star. But he won, and once he won, then the tribalism kicked in, and the party coalesced around him, and now he's a real juggernaut, and it's a deeply concerning challenge for the polity.