He has denied it, over and over he has said its garbage. That should be enough.
My point was that once should have been it and done. Accusations like this are awful and simply impossible. The more airtime you give them, the more life they have. It should be, “I’ve already addressed that issue, next question” and move on. He just cannot pass up the opportunity to spread the garbage about Trump. At this point, he could pull this whole campaign back out of the gutter, but he chooses not to.