The Untruth Social thread focuses on the dishonesty of Trump and his administration, and the Trump and mental illness thread covers his psychopathology, but I think we also need a thread focusing on his stupidity.

No better place to start than with the 2018 Twitter quote that inspired the OP title:

Actually, throughout my life, my two greatest assets have been mental stability and being, like, really smart. Crooked Hillary Clinton also played these cards very hard and, as everyone knows, went down in flames. I went from VERY successful businessman, to top T.V. Star, to President of the United States (on my first try). I think that would qualify as not smart, but genius….and a very stable genius at that!

That quote is its own best refutation, because no one who was truly a stable genius would be stupid enough to say that he was “a very stable genius” and “like, really smart.” Trump is neither, and this thread will soon be full of examples proving it.