I believe Franklin Pierce is often considered the worst US president ever, but that can be rivaled with George Bush II. Its hard to say the smartest when you're competing with great men like George Washington, Abraham Lincoln, FDR, JFk, ect. though, so its hard to say on smartest :)
Smartest-Bill Clinton. He listened to his advisors that were economic geniuses. Dumbest. I forget the name, guy that got into a duel and lost. Middle finger to the liberals that put G.W.Bush as the dumbest. Just because he wasn't smart didn't make him an idiot.
I guess we're all pretty much agreed that Dubya was the dumbest. It's much harder to pick the smartest-luckily, we've had lots of smart presidents. Lincoln and Jefferson come immediately to mind, but what about Eisenhower, who warned us about the military-industrial complex long before anyone else was thinking about it? Or LBJ, who passed more civil rights legislation than any other president? This was an interesting question!
Dumbest: Bill Clinton. He can't get high right & in spite of having a daughter (??) doesn't know what constitutes "sex"! Smartest: Lincoln & Reagan (tied). Why? Both were men of tremendous integrity who never gave it up in spite of pressure & working for/with a plethora of crooked politicians!!