Michael D'Antonio is author of the book "Never Enough: Donald Trump and the Pursuit of Success" (St. Martin's Press). The opinions expressed in this commentary are his. View more opinion articles on CNN.

(CNN) Though the White House had drafted a statement on the death of John McCain, it was not released. Instead, President Donald Trump tweeted "sympathies and respect" to the family, saying nothing of the contributions of the widely esteemed senator.

Nothing could tell us more about the character of the petty man in the White House than his weekend display. As tributes filled the news media -- many from McCain's political opponents -- Trump showed he lacks the common decency required of his office. After years devoted to dividing the country, he could not play the role of political healer, even to honor a man from his own party.

However, in a perverse way, Trump provided a service to the nation. He called attention to the difference between himself and McCain, giving us a chance to reflect on their disparate leadership styles.

Think of this exercise as the political equivalent of the old tale of the tape that newspapers routinely published to predict the outcome of a boxing match.

Courage: McCain demonstrated it in abundance, from his Vietnam war service in his youth to his final battle with brain cancer. Trump, : McCain demonstrated it in abundance, from his Vietnam war service in his youth to his final battle with brain cancer. Trump, who claimed bone spurs to avoid military service, once tried to show bravery by breaking with his party on gun control but retreated in less than two weeks.

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