Hillary wasn't worthy of her nomination, and yet here we are. Jeb Bush attempted the same thing, but failed very early on.

You're failing to recognize that GOP establishment hates Trump just as much as Democratic establishment does. They would rather fail themselves than let him win, because they feel it in their guts that if he wins, he won't keep them around for long. He's an anti-establishment candidate. That's the platform he ran on, and that's the platform he will run on in 2020 (and likely win again, unless Democrats can suppress their utter disdain for rural, working class voters).