One of the guys in political science and I just got in an argument about who was the smartest president. I went with Thomas Jefferson, Jimmy Carter, and James Garfield (who apparently could simultaneously write in Greek with one hand and Latin with the other).
He was arguing for Abraham Lincoln and Teddy Roosevelt. I would agree that Lincoln and Roosevelt were bright and effective, but I'm not sure their IQ scores would be in the genius range.
Perhaps this is a different point of view between historians and political scientists. Maybe they think to be smart a present also has to accomplish something, while historians assume if a president is REALLY smart he will probably be ineffective.