It is generally a good list but I strongly disagree with two choices. He ranks Lincoln as a"great president" and Harding (along with Dubya) as only"average."
While this gives Harding more credit than most historians, I would put him at least in the"above average" category. Harding had an excellent civil liberties record (he released Wilson's political prisoners) and was good on civil rights (even better than Coolidge, Jon!). He cut taxes and spending and signed the Washington Naval Treaty (the most radical arms limitation agreement ever). As Mayer notes, Teapot Dome was a trivial scandal compared to those of many recent presidents. Harding was certainly better than John F. Kennedy, who Mayer ranks above him.