Based on all my conversations this week, here is how I think it will play out.
If Trump can go the next two weeks without unforced errors and can do interviews along the way without embarrassing himself or the party, his nomination is assured. Trump has to be able to go out, without the Teleprompter, give speeches, and also give press interviews. If he hides in a bunker for the next two weeks, he will damage himself with prominent Republicans and donors. They need to see that he really is growing up and toning down.
If Trump can do that, he is the nominee, and not just the presumptive nominee.
But if Trump cannot control himself and exercise self-discipline in the next two weeks, the Republican convention is going to spiral out of control and look to a savior. That savior is most likely going to come from Wisconsin. It will not be Paul Ryan, but Scott Walker.