Maybe something to do with anti-semitism?
Sleeping with an underage girl is also a possibility.
I think this is the real most likely one. Listen to the way he talks, there's no way he hasn't bought/raped an underage girl in his life. The only question is whether they have the proof. Granted, half of white men will still find that heroic, but it'll do the damage to the sane.
Good God, don't say it.
That would be the ultimate damage to not only his campaign, but to trump's business, his "name," and his family.