Alzheimers will be a hard sell as Trump, as far as I know, shows no hint of dementia.

Instead, if in fact they need a reason for him to resign, it will be something emanating from his narcissistic egomania, a two year olds equivalent of hiding in a dark place, hugging his blanket and sucking his thumb.

Most likely, though, convinced by the power of Comey's coming open testimony before Congress, Ivanka and her husband, ultimately, will talk him into resigning before impeachment proceedings commence. Stubborn as he is, he listens to them.

Their motive will be to keep their 'hero' from crumbling in public. Plus, quite possibly, a more noble one, that of protecting the Office of the President.

Imagine, they've never seen their father in any environments but real estate and TV before now, where he was a knight on a white horse. It must be devastating for them to see that hero slowly disintegrating, day by day it seems, from self-inflicted wounds of incompetence.