Well, there's the new (and probably enduring) Trumpscuse:
"When the President does it, it's not illegal."
That one will stick around in various forms for a while, I think. It's clear from Lewandowski's book that Trump is deeply insecure about literally everything about himself; he likes surrounding himself with Harvard graduates so he can boss around people smarter than him, for example, and "prove" he's better "at life" than they are. The same compulsion drives him to surround himself with generals.
Dowd's latest piece of legal nuttery plays right into that drive to brag about how special he is. After all, other people may be richer or smarter or better-looking than him (and that last one matters to a disgusting degree with him), but no one is Presidenter than him -- and I have no doubt he will eventually degrade into putting it that way, because he's unraveling fast.
"Hillary did it too" may fade, "locker room talk" may ring even more hollow than it does now, and even the great "witch hunt" may one day fall out of favor, but "I am the President and can therefore do nothing wrong" will be on his Twitter feed for the rest of this administration and beyond.