Commentary Every so often you read about a survey in which scholars rate the performance of previous American presidents. A good example is one recently conducted by C-SPAN. You can see its presidential rankings here. The C-SPAN survey awards the top two positions to Abraham Lincoln and George Washington, respectively. There are some good reasons for placing those two presidents at or near the top. Below that, however, the C-SPAN ratings—like the results of most other surveys (such as this 2015 one from the Washington Post)—are largely detached from reality. For example, is it really credible that the top 20 presidents of all time should include six of the last seven Democrats? Yet that’s where the C-SPAN results place them: Franklin Roosevelt ranks third; Harry Truman, sixth; John F. Kennedy, eighth; Barack Obama, 10th; Lyndon Johnson, 11th; and Bill Clinton, 19th. The only modern Democrat not to make the top …