Just quick food for thought.
There are many things that separate great leaders from awful ones.
But I would posit that the greatest separation is the capacity for learning and allowing events to change your mind. It's not uniquely American, but nonetheless I think it is fair to say that those two individuals considered the "GREATEST" Americans over the generations, Washington and Lincoln both made a LOT of mistakes, and were quite flawed. This is especially true when it comes to military questions and policies. The mythological Washington is far from the actual figure, and the actual figure, who was hardly a military genius and importantly knew he wasn't suffers for it -- he rarely won a military battle, yet managed to win a war. Lincoln's ability to adapt and ultimately both lead and follow on the important questions of the War make him arguably the Greatest President, Washington's ability to reflect make him perhaps the Greatest American.
Now compare to George W. Bush who is sure he is right about everything and has no capacity to adapt to fuckall.
Yet, he is not the first, or only American politician (see McCain, John & Lieberman, Joe) to not learn this lesson -- simply the worst. The lesson is, the greatest leaders admit their own failings and learn from them.
But not Dear Leader, making him the first real challenger to the title of WORST PRESIDENT EVAH, since Warren Harding stroked out of office more than 80 years ago.