Corbett is absolutely correct. Sorry, Delta, but you're wrong. Especially if you think Lincoln followed the Constitution. In actuality, he destroyed it.
One could cite a thousand instances where he violated the Constitution. But the broader, conceptual view is that he transformed a Confederacy (that would be ALL the states--North and South) in which the states were sovereign, and only yielded to the central government a few, jealously-guarded powers, into a single nation, in which a central government tyranny rules over the states.
Unquestionably, the worst President ever. No other is even close.