Hillary is looking at the camera well in front of tRump.
Obama reads a lot, probably with glasses, and is accustomed to looking through the bottom of his lenses. Without glasses he tips his head back.
tRump is there to annoy the Bushes.
But, I'm guessing.
Alex
"There is a cult of ignorance in the United States, and there has always been. The strain of anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that "my ignorance is just as good as your knowledge."
-- Isaac Asimov