This refusal to recognize the unwritten rules that govern us, so evident during Mr. Trump’s failed attempts at humor, is a central feature of his presidential tenure thus far. If a leader does not understand the idea of benign violations, blatant violations inevitably occur.

Humor helps us recognize, and cope with, life’s absurdities. While I certainly never asked him directly, I got the sense Mr. Obama appreciated that the modern American presidency is in many ways a fundamentally bizarre proposition. Commanders in chief must accept the responsibilities that come with holding the fate of the world at their fingertips, while simultaneously admitting that they are only human. Presidents can either laugh at the strangeness of their circumstances or be consumed by them.

Without the qualities that laughter both demonstrates and fosters — a willingness to find common ground, the respect for agreed-upon norms and the awareness that we are all only human — Mr. Trump’s attitude toward the presidency is defined by the one characteristic that remains: a lust for power. And this is perhaps the most troubling thing about what passes for a sense of humor with Mr. Trump. Thanks to the power of the internet, there is proof that our president has indeed laughed at least once. This was during a campaign rally in January, when Mr. Trump’s speech was interrupted by a barking dog.

“It’s Hillary!” an audience member shouted. And the candidate tilted his head back, opened his mouth wide and laughed without reservation, quite possibly for the first time in his political life.

This documented incidence of Trump laughter is as illuminating as all the grim smiles that preceded it. For they reveal a president who is constantly, endlessly preoccupied with status. A craving for power isn’t unique to the politician currently holding the Oval Office — on the contrary, it is more or less a requirement for entry into the field. But a craving exclusively for power is.

It is not too late to undo the damage our humorless president is causing to American democracy. Democrats (and some Republicans, these days) are already thinking about who might replace him in 2020. And if there is one thing all Americans should be able to agree on, it is this: Whomever we nominate to replace President Trump, it is time to put an easy laugh back on top of the ticket.