This is a fight he can't win.
Why is he doing this? There's no way it can turn out well for him, except maybe to reassure his dwindling and increasingly panicky base. No Democrat, and few Republicans will believe this.
Maybe someone is encouraging him to do this, for their own motives; either some Dem trying to smear the GOP or a Republican trying to replace Trump with someone more to his liking.
If that's not it, if he's just making this up in some vain attempt to derail the Russiagate investigations, then he is truly non compos mentis and striking out randomly from sheer paranoia.