You can't really tell how long his presidency lasts. Two term limit is just a rule that can be changed with help of judiciary branch. If Americans want him for a third term who'd object?
Trying to reinterpret "No person shall be elected to the office of the President more than twice" to allow for that would be quite a spectacular feat of jurisprudence.
It's just 22nd amendment. Can't be more important than the will of the nation. The only question is do the Americans like Trump as much as they like booze or can it be at least made to look like they do.
Theoretically, if changes were put into place to allow a run for a third term (which is highly unlikely given age), then that also opens the door for someone like Obama running again.
People don't seem to understand that even Trump's judges still see themselves as JUDGES. They're not going to just make stuff up that's not in the law, and there were several instances in his first term where his own SCOTUS Justices told him to pound sand. It's not so simple as "nominated by Trump == inherently corrupt," much as he'd like it to be that way.
Only saving grace. Although Putin is just 6 years younger and his strive to leave legacy already messed up the world. One can only wonder what mess will Trump's attempts at leaving legacy cause.
I am not talking about the legacy. The legacy will live one - I mean technically the world has changed post 2016 and it has not gone back since then. And it won't.
With 2024 it might change the landscape more.
