Belz...
Fiend God
It strikes me as exactly the sort of petty, spiteful thing Trump would do. Obama mocked him and made important people laugh at him whilst the whole world was watching; for someone with narcissistic personality disorder that was the worst thing that could possibly happen to him. I also have no trouble believing Putin has a tape of it. What I don't believe is that it's an effective blackmail tool. Show that tape to most of Trump's core supporters and they'd cheer.
Nah, if there's any Kompromat, it's that Trump's actually destitute; that he's not the wealthy playboy he says he is; that the money he has is entirely beholden to Russian interests. I think that revelation would destroy his fragile ego more than anything else.