Disdain for the new president was palpable within the political, intellectual, and social establishment. Many members of his own Republican Party found his ascendancy horrifying with the party chairman renouncing “that damned cowboy in the White House.” Newspapers censured him as “impetuous, impatient, and wholly lacking in tact.” One of the nation’s leading writers sputtered, “we have never had a President before who was destitute of respect for his high office; we have had no President before who was not a gentleman; we have had no President before who was intended for a butcher, a dive-keeper or a bully.” Critics lined up to condemn his childish impulsiveness (“You must always remember that the president is about six,” noted a weary foreign ambassador), his bad manners (“he lectures me on history as though he were a high-school pedagogue,” complained one of America’s leading historians after a White House dinner), and his unseemly aggression and bluster (an acquaintance described him as “still mentally in the Sturm und Drang period of early adolescence”). The new leader of the United States, in the opinion of many of the nation’s elite, was a bellicose, bloviating blowhard.

No, this is not the latest excoriation of President Donald Trump but one aimed at a predecessor who, although separated by a century and a quarter, shared many of the same impulsive political traits: Theodore Roosevelt. The parallels between the two men are striking. Like The Donald, TR bucked the Republican Party establishment, assumed the presidency in unexpected circumstances — the former from a stunning election upset and then an equally stunning political comeback, the latter from the assassination of his predecessor — and then quickly came to dominate the political scene as a maverick leader. Likewise, the two chief executives displayed a set of personal characteristics that simultaneously fueled their success and triggered accusations that their outlandish conduct violated every norm of...