“The tapes are the real man — mean, vindictive, panicky, striking first in anticipation of being struck, trying to lift his own friable self-esteem by shoving others down,” Gary Wills wrote of Richard Nixon in the 2017 preface to his book, “Nixon Agonistes.” Wills added, perhaps unfairly, that “Nixon’s real tragedy is that he never had the stature to be a tragic hero. He is the stuff of sad (almost heartbreaking) comedy.” The passage comes to mind as we close out Donald Trump’s annus horribilis, during which he supplanted Nixon as the saddest figure in post-presidential politics. The Jan. 6...