Aside from Trump’s desire to reduce scrutiny and accountability, there are other theories for why Trump finds it so difficult to denounce Nazis and other racists without getting diverted into rants about journalists.

One is that he has always had a soft spot for racists, ever since as a young real estate developer he was sued by a Republican Department of Justice for systematically discriminating against blacks. Over the years he has also been quoted as saying that “laziness is a trait in blacks,” declined to distance himself from the Ku Klux Klan and periodically retweeted posts by neo-Nazis (including one from an account called @WhiteGenocideTM with a photo of the founder of the American Nazi Party).

Another theory (these are not mutually exclusive) is that Trump is simply a thin-skinned narcissist who shares the white supremacists’ sense of victimization. It was striking that in Tuesday’s speech in Phoenix, he seemed to believe that the biggest victim in Charlottesville was not Heather Heyer, who was murdered, but himself.

Yet another possibility, which previously was mostly whispered but is increasingly openly discussed even by members of Congress, is that our president is mentally unstable.

The causes of Trump’s bizarre behavior may be difficult to disentangle. But I hope that you, as members of the public, will understand what is at stake in his assault on the media. This is not about reporters and the mistakes we make, but about institutional checks on the presidency.

We appreciate, not always gracefully enough, the public’s efforts to keep us honest. We also are grateful for the outpouring of subscriptions to news organizations, and the support for organizations like the Committee to Protect Journalists. The irony has been that the more Trump vilifies the media, the more the public has rallied around us — and, finally, this is helping us gain a better business model. Since Trump was elected, the stock price of the Times Company has risen by almost two-thirds. Thank you for your assistance, Mr. President!

This is an extraordinary moment in our nation’s history, for we are enduring an epic struggle over the principles on which our country was founded. These include the idea that a flawed free press is an essential institutional check on flawed leaders.

So may I humbly suggest that when a megalomaniacal leader howls and shrieks at critics, that is when institutional checks on that leader become a bulwark of democracy.