It was hardly surprising that, on the night he was being impeached, President Donald Trump was raging on stage at one of his raucous political rallies, this time in Battle Creek, Michigan, mocking and denigrating anyone and everyone who doesn't bow to him. But he then went even further, showing that his cruelty really has no limits.

He imitated Rep. Debbie Dingell, D-Mich., whose husband, former Democratic congressman John Dingell, died in February at age 92 of complications from prostate cancer. Trump launched into a sing-songy, whispery rendition of what he says she asked him — to lower flags to half-staff — and then her grateful response, which included (according to Trump) her saying that her husband was looking down from above.

Then he aimed for the jugular, saying that maybe John Dingell was "looking up" from below. So, to be clear, the president of the United States went to the home state of a congressman who died not that long ago and snarked that Dingell might be in hell. For probably the first time ever, some in his crowd of die-hard fans groaned.

Debbie Dingell, displaying the sort of dignity that is alien to Trump, responded by reminding us all what grief looks like, and how facing the first holiday season without her husband is a wound that cuts deep. She then noted that Trump made the wound deeper, which sadly was probably music to his ears. Being publicly attacked is a disorienting experience, one I am unfortunately familiar with. It doesn't matter how you feel about the person who has decided to deride you or a member of your family, you think about the millions of people who are listening, perhaps laughing, and the humiliation burns deep into your bones.

When my father died in 2004, I happened to come across online comments saying he should have died sooner; others rejoiced that he was dead. A comedian on television mocked the fact that there was nearly a week filled with somber events and services, including my father's body lying in state. The comedian ridiculed the plans and said something to the effect, "We get it. He's dead. Enough already!"

Of course, none of that compares with what Trump said about John Dingell, who had been the longest-serving member of Congress in history, representing Michigan for 59 years before retiring in 2015. My heart goes out to Debbie Dingell.

Trump has assaulted numerous people at his rallies — a Gold Star family, a disabled reporter, various women, political rivals. Maybe some of those in his audience on Dec. 18 finally began to perceive that his cruelty is limitless, his sense of decency nonexistent.

"What the president misunderstands," House Speaker Nancy Pelosi, D-Calif., said the next day, "is that cruelty is not wit."

I disagree. I think he understands perfectly the power of cruelty to inflict deep wounds. He wasn't aiming for wit. He wouldn't bother with wit when he can aim for the heart of a widow and try to break that heart again.

Patti Davis is an author, most recently, of the novel "The Wrong Side of Night," and the daughter of former President Ronald Reagan and First Lady Nancy Reagan.