Hayward takes the approach of rating the presidents based on their job description, which is basically:
- Preside over the military as commander-in-chief
- Execute the laws passed by congress
- Ensure the laws passed are constitutional (if not, veto them)
- Nominate Supreme Court justices
Furthermore, the President must take this oath of office:
"I do solemnly swear (or affirm) that I will faithfully execute the Office of President of the United States, and will to the best of my Ability, preserve, protect and defend the Constitution of the United States."
Hayward's book is important because it reviews each of the presidents, starting with Woodrow Wilson, grading them according to how well they performed their job description and upheld the oath of office. He starts with Wilson in 1913 because it was Wilson who first significantly expanded the job of president beyond the job description laid out in the Constitution. Before Wilson, presidents performed their duty by commanding the military in times of war (e.g. Lincoln, Madison) or keeping the congress in check by vetoing unconstitutional laws (Hayward gives wonderful examples from Madison, Pierce, Buchanan and Cleveland).
I agreed with most of Hayward's ratings for the early presidents. But for the presidents since Reagan, I thought he had a Republican vs. Democrat bias which wasn't supported by the examples he provided. Since this book was published in the election year of 2012, I believe part of the purpose was to get people to vote against Obama and so the later rankings had more partisan bias. But this doesn't detract from the value of this book which is the assessment of how the U.S. Presidents of the last hundred years lived up to their duty to protect the Constitution.