Donald Trump is the worst President since (restarted with Harding added):

[Kodak]

I believe Nixon edges out Bush and Trump for the misery he unnecessarily inflicted on the rest of the world. Bush also failed to start a constitutional crisis, although the rest of his domestic agenda was much worse than Nixon's.

Trump still has plenty of time to outdo Nixon on both fronts.

[Amenhotep Bakari-Sellers]

Nixon is a good analogy, given Wikileaks unauthorized access to Democratic emails in Dem headquarters. Nixon broke into Dem headquarters due to Watergate

[Inmate Trump]

A good argument that W was worse, but I don't think so. The outright treason IMHO outdoes even the idiocy of the Iraq War.

Beyond that, I'm struggling to see how even A. Johnson was as bad, so I'm forced to say Buchanan.

Exactly.

If a president commits treason, that sort of makes the actions of his predecessors pale in comparison.

Trump is worse than Dubya, case closed.

[pbrower2a]

Not that I think Coolidge worse, all in all, I see Coolidge doing great damage in his insistence upon German repayment of WWI reparations while Germany was undergoing hyperinflation. The hyperinflation and reparations contributed to the rise of Satan Incarnate in Germany.