Brooks Simpson, the noted biographer of Ulysses Grant, makes some good points about the problems with presidential ranking polls. Among them, what are we supposed to evaluate?
I also wonder about the criteria for evaluation. First, are we evaluating a president’s effectiveness in achieving his agenda, without regard as to what that agenda might be? Take the case of James K. Polk, who was very effective in meeting his goals. Does that make him a great president? Or take the more complicated case of Andrew Johnson. The seventeenth president is currently considered one of the worst chief executives. Certainly his presidency was a damaging one. But was it ineffective, or was he something of a Tim Tebow in the White House, who got the job done in an ugly fashion? After all, Johnson wanted to preserve white supremacy while restoring the Union. One could argue that his obstructionist behavior undermined efforts to pursue a more fundamental reconstruction of the nation that established a sounder foundation for the future of the emancipated. Yes, a Republican-controlled Congress passed legislation and two constitutional amendments, but it also rushed to restore civil government and spent a great deal of energy in seeking to handcuff Johnson. The result was the construction of a structure on unsound ground that soon collapsed in the 1870s.
Is the criteria getting your agenda accomplished? Fitting the moral strictures of 2012? Leadership? Ability to handle a crisis? Simpson also notes that these polls way oversample biographers of famous presidents, leaving voices evaluating, say, William Howard Taft way behind.