Among the more revealing moments in the ongoing White House nervous breakdown came in chief of staff John Kelly's initial defense of staff secretary Rob Porter. As accusations of domestic abuse against Porter became public, Kelly pronounced him a man of "true integrity and honor."

I have never been in the military, and have great respect for Kelly's distinguished service. But I suspect that, for most people in uniform, this is not what they mean by "honor."

I did, like the rest of the incoming White House senior staff in 2001, take the oath of office in the East Room of the Executive Mansion. The moment, at least for me, was less joyful than sobering. History hangs heavy in that place, where Abraham Lincoln, Franklin Roosevelt and John F. Kennedy laid in repose. Where Lyndon Johnson signed the Civil Rights Act of 1964. The setting, the moment and the words — "I do solemnly swear ..." — evoked a mix of awe, pride and fear of being unequal to the honor.

This experience as a staffer, I suspect, helps explain the intensity of my reaction to Donald Trump. The institution of the presidency does not require perfect men or women. But by even the most generous standards, Trump is a figure of monumental smallness. He describes himself in terms that would have embarrassed King Louis XIV. He conducts himself with the decorum of a spoiled and nasty child — lashing out at enemies, elevating lackeys, treating professionals at the FBI or CIA like minions, blurting out conspiracy theories and obvious lies. He regularly brings the presidency and the country into disrepute. And the White House staff — leaky, incompetent, embittered, backbiting — has generally followed his example.

Most Americans probably don't share this sense that Trump is defiling something noble. For many Trump critics, his misogyny, nativism and religious prejudice are more urgent indictments. For many Trump supporters, the whole idea of nobility in politics is a sham. They can point to Richard Nixon oozing anti-Semitism on the secret tapes, or Bill Clinton having a dalliance in the private hallway near the Oval Office. In this view, political honor is an illusion, dignity is softness, and reverence is pretense. Trump, in refreshing contrast, acts and talks like someone from the real world.

I would dispute the assumption that racism and verbal cruelty are characteristic of average Americans. But in this case, cynicism is also a form of historical blindness. American presidents have often risen to extraordinary moral leadership. Consider Franklin Roosevelt pushing a reluctant country toward support for Great Britain, with the future of liberty in the balance. Or Dwight Eisenhower sending in the 101st Airborne to integrate Central High School in Little Rock. Or Ronald Reagan insisting that the Cold War could be won, because the yoke of oppression does not fit human shoulders.

These leaders believed that America has some special destiny in the world. And they conducted themselves in a manner consistent with that calling.

Presidents are not, in the end, judged primarily by the tax cuts they pass. They are measured by the standards JFK set out in his farewell to the Massachusetts Legislature in 1961: "Were we truly men of courage ... were we truly men of judgment ... were we truly men of integrity ... were we truly men of dedication?"

For some presidents, these virtues were a guiding passion; for others a political facade. This president has abandoned even lip service to these ideals, conducting himself like the CEO of a shady casino company seeking to build his fortune and destroy his competition. Which is exactly what Trump has always been.

By his conduct, the president (metaphorically, as far as I know) puts his muddy boots up on the Resolute Desk and spray paints graffiti on the Roosevelt Room wall. He is vandalizing the one house he cannot buy or own.

This is not mere mysticism. Most important institutions are protected and empowered by esteem. To the cynic, a judge is an average woman in a robe; a general is a poser in a costume; a priest is a balding man with sweat staining his armpits. But however accurate these depictions, they are not true. Because of the institutions they serve, these people represent the rule of law, the triumph of duty, the presence of God.

The institution of the presidency will survive Trump, as it has other mediocrities. But the office deserves an occupant of true integrity and honor.

— Michael Gerson's email address is michaelgerson@washpost.com.