Said AprilApple in the comments to the previous post, which sets the scene for tonight's debate.
He can. The question is whether he decides that tonight is the night for him to play Adult in the Room (a role John Kasich chose for himself in the last debate). Trump still must squelch Rubio and Cruz and he hasn't yet seen whether either of them or both will decide on the Adult in the Room gambit. I think perhaps all 4 men will go for an elevated presidential demeanor. If so, it will be funny to see how it looks on each of them.