Although I’d place fairly long odds against this thermonuclear tactic, there’s also the possibility of piecemeal skirmishes for delegates. In South Carolina, for instance, delegates might unbind themselves on the pretext that Trump withdrew his pledge to support the Republican nominee. Remember those chaotic Nevada caucuses that Trump won? They could be the subject of a credentials challenge. There could also be disputes over the disposition of delegates from Marco Rubio and other candidates who have dropped out of the race. A final possibility is “faithless delegates,” where individual delegates simply decline to vote for Trump despite being bound to do so by party rules. It’s not clear whether this is allowed under Republican rules, but it’s also not clear what the enforcement mechanism would be.By convention time, we'll know what the margin is. If Trump has the majority, 1,237, or a bit more, there is still a game to be played. If he has only 1,237, the majority is lost if just one of those delegates flips, for any of a range of technical or political reasons. Trump has to keep wrangling his delegates, and how will he do that among these "mostly dyed-in-the-wool Republican regulars and insiders"?
Trump has a lot of pride in his knowledge of how things work in the real world — how China is "killing us" in these trade deals, etc. etc. — other politicians are naive and he's the one man who can bring expertise in handling wily people who are trying to take advantage. But the real world of this delegate game has brought him up short. It must really hurt his pride, privately, and it hurts his image publicly.
Remember how, in his meeting with the RNC about the wrangling of the delegates, "Mr. Trump turned to his aides and suggested that they had not been doing what they needed to do." That's a nightmare for him. He suddenly sees the dimension of the game he's been so proud of playing so well, and he's ill-equipped to enlarge the operation into something that can work in the coming phase. I'm picturing him losing heart, losing steam. He got so inflated about the polls and how much he'd been winning. And now he sees he's only winning in Part 1, and he didn't even understand Part 2. He doesn't have a team that could play Part 2.
Trump is going to have to rely entirely on a direct appeal to the people. He'll argue that it's outrageous and undemocratic to deny him the nomination. But the decision will be made at a convention where there's a vote — that's democracy too — of a set of delegates. And a majority of them are going to be opposed to him — even if a majority are pledged to him.