I'm more worried about Hillary being her own worst enemy than I am about Trump doing something great. Trump gets a lot of flack for always getting in his own way, but, in reality, Hillary does a lot too.
She puts a foot wrong more than a good campaigner would, yes. But she doesn't stuff her leg down her throat, chew on it, and then try to say "there's nothing in my mouth" around a cheekful of kneecap.
I'm more worried that some big external event comes along that hurts her and helps Trump: a major terror attack or other foreign policy disaster where Trump can say "I would have stopped it" and idiots will believe him.