Donald Trump wants people to think he’s a winner. So why does he act like a loser?

Winners convey a sense of effortless superiority. They don’t have to work at it. You just know they’re above it all. If someone tries to criticize them, it’s beneath their dignity to worry about it. It’s just a little speck they brush off their shoulder.

The Brits are good at that, Boris Johnson especially. We still don’t know how things will turn out there, but I expect his aplomb will carry him through. “There are no disasters,” he once joked. “Only opportunities. And, indeed, opportunities for fresh disasters.”

Trump? He’s got the thinnest skin of any politician — and that conveys weakness, not strength. It was why he had such a miserable, no good, horrible month of August. When you attack a nonentity like Beto O’Rourke, you build him up and diminish yourself. And that goes double for Debra Messing.

As for going after an entire city — an American city at that — you made us feel sorry for Baltimore. Somehow, Trump improbably managed to let Democrats turn his attack on Democratic misrule to their advantage.

We saw Trump as weak, and that’s reflected in his poll numbers in August. About 30% of Americans don’t mind Trump’s bluster. Then there are 45% who haven’t figured out whether Trump is Hitler or whether he’s worse than Hitler.

But it’s the remaining 25% who decide elections, and we’re creeped out by the nastiness and show of weakness.

We’re also tired of the “whataboutism” and of being reminded about the nastiness on the other side. Our politics have become a ping-pong game, when one side matches the worst the other side sends its way.

Trump mocks the Democrats, and they call him a racist. It’s tit-for-tat. Historian René Girard labeled this mimetic rivalry, with good paid back for good, and ill for ill. Except it’s never good here.

We weren’t always like this. In American politics, sunny ways are usually winning ways. Barack Obama seemed to enjoy himself on the campaign trail, as did George W. Bush and Bill Clinton. The same can’t be said for John McCain in 2008, Al Gore and Bush 41.

Matched against malaise and Jimmy Carter, Ronald Reagan charmed Americans with his wit. FDR personified sunniness, and Teddy Roosevelt thought that political campaigns were great fun. Abraham Lincoln embarrassed polished Republicans with his corny jokes, but his listeners loved them.

In 1968, Hubert Humphrey called sunniness the “politics of happiness.” That’s how he campaigned and was widely mocked for it. We were in the middle of the Vietnam War, and the Democratic Convention that year was marked by rioting. Martin Luther King and Robert Kennedy had been assassinated, and here was Humphrey telling us he was happy?

But matched against Richard Nixon, the darkest candidate ever to win the presidency, and in spite of George Wallace winning five states and 46 electoral votes, Humphrey’s late surge brought him very close to victory.

René Girard hated mimetic rivalries, where nastiness is repaid with nastiness, and struggled to understand how cycles of reciprocal animosity could be broken.

His answer can be taken from the Epistle to the Romans: Leave revenge for God, said St. Paul. “If thy enemy be hungry, give him to eat; if he thirst, give him to drink. For, doing this, thou shalt heap coals of fire — anthrakas pyros — upon his head.” Show him how little you care about his ill opinion by being nice to him.

It’s a bit late for a personality change for Trump. He doesn’t do sunny. Nobody does today. But he might lay off the nastiness if he recognized that you don’t communicate superiority by answering your opponent in kind. Instead, you do so through an unruffled imperturbability, brushing the dust from your shoulder and perhaps cracking a joke.

In last January’s State of the Union, Trump showed that he can be gracious, and we need a bit more of that. Elijah Cummings showed a bit of class when he invited Trump to Baltimore; Trump should reciprocate by offering to take him to brunch at Miss Shirley’s in that city.

I recommend the pancakes.

F.H. Buckley’s next book is “American Secession: The Looming Threat of a National Breakup,” due in January.