Trump's lead in the polls is stabilizing and he's got control of the primary at this point. The GOP establishment wants to dislodge him, but his threat of a 3rd party run means they have to convince people he's not an option.
It comes down to the first debate. The rest of the candidates should all share notes and study with each other prior to the first debate. They should share expertise on various topics. They should share knowledge about topics that Trump probably doesn't have. Then the moderator should ask specific questions about those topics to everyone. Everyone will be able to answer knowledgably about the topics except for Trump. This will reinforce the notion that Trump is the least informed candidate on the stage. This tactic would likely end his campaign for the GOP nomination AND cost him enough support so that he cannot mount an independent run either.
For Trump to win, he has to recognize that he is truly the leader of the field and that his party will stab him in the back if it can....and do what is appropriate - - namely, not show up at the debates. He has absolutely nothing to gain from debating the rest of the clowns on that stage. If he shows up, it will be a long long nite of defending his record from everyone else. There is no point in subjecting himself to that. Trump would be better served just taking full command of his campaign and not debating anyone else.
If Trump doesn't debate anyone, he could carry this show all the way to the end.