That depends. If he plans to run in 2020 he may be trying to quell the criticisms of those who feel he is not doing what is best for the party. If he has no plan to run he should stay as far as he can get from the circus sideshow that is the Donald Trump campaign.
@Vulcan Yeah, but now his 2020 opponents will be able to pull up video of him calling Trump totally amoral, a pathological liar, etc., and the convention speech video, and they'll say he isn't a man who keeps his word or who acts on principle. He just screwed himself, and for nothing.
Well, I'm glad I'm not married to him. If my husband were in his position and I were the one smeared by Trump, Donald would have ended up with teeth on the floor instead of an endorsement.