When Trump hurls accusations against Hunter Biden, he instinctively knows that he’s pressing his current opponent’s greatest vulnerability, one achingly depicted in a profile of Hunter by The New Yorker’s Adam Entous. Having survived the car crash that killed his sister and mother, Hunter has lived with the scars that make everyday life a seemingly unwinnable affair. As a grown man, Hunter would hole up in his Washington, D.C., apartment, leaving only to buy bottles of Smirnoff. His father, then the vice president, would call several times a day; he would show up unannounced to prod his son out of his darkest confines, telling him, “I need you. What do we need to do?”

The subject of Hunter was a source of such profound sadness that many aides disliked ever raising it with the vice president, even if they might have had misgivings about the younger Biden’s professional dealings. One source told Entous that difficult conversations about family would cause Joe Biden to get “deeply melancholy, which, to me, is more painful than if someone yelled and screamed at me. It’s like you’ve hurt him terribly. That was always my fear, that I would be really touching a very fragile part of him.”

That fragile part of him is what Trump is furiously poking now. He’s cruelly lashing Biden, not to explain the relevance of an esoteric scandal that doesn’t directly indict the ethics of his opponent, but because he seems to hope that his raising the subject will induce an unbecoming outburst of emotion onstage.