The worst American President ever, serving from 1857-1861, and that's saying something when you have George W. Bush, Warren G. Harding and Franklin Pierce. Seven states succeeded from the Union under his Presidency. His excuse for inaction was: I do not have the constitutional authority to do anything.
Niall: Seamus, did ya hear that South Carolina has left the Union?
Seamus: Aye, tis a major problem, what is James Buchanan doing about it?
Niall: He says he doesn't have the constitutional authority to send troops!
Seamus: Boy, that Buchanan is really fucking up!