if/when he resigns, he and his family are off limits forever. There would be some clamoring but to no avail. That's one fo the perqs of the job.
Rep members of Congress are pretty powerful people, too. They are not going to lose their positions nor let Potus do a Rep party takedown just for his sake. I don't know whom will be the person to take that long walk to tell him.
However, it's looking more and more likely with every passing day now…
He's going to have to resign. The sooner the better for November.