1. Wilson
2. Tyler
3. Pierce
4. Jefferson
5. George W. Bush
While Buchanan was not a particularly good president, one can't really say he made things much worse than they otherwise would have been, which is why he doesn't make my worst 5 list. If either Tyler or Pierce had had a full eight years they might have been able to displace Wilson from my top 5, but they were both bad enough in their first term to preclude getting a second so we'll never know.
Please explain that. As bad as the Ograbme was, it can't make him worse than Buchanan.