It was at dinner a month ago in a Manhattan restaurant. Old friends who live far apart had come together on a leisurely spring night. But it turned testy fast.

I note here that the style of anti-Trumpers is often highhanded and manipulative, while the style of pro-Trumpers can be brutalist and patronizing. One couple, my old friends, had been for Marco Rubio and then John Kasich and were now enthusiastically for Donald Trump. Last year they hadn’t liked him, but now they thought wait, he’s the donkey we need to knock over the barn.

There was another couple, intellectuals, also pro-Trump but from early on, and with a certain edge. The lady of that couple, disliking recent criticism of Mr. Trump in these columns, was not jolly but defensive. She leaned in and said that what I didn’t understand was that Donald Trump is Ronald Reagan—an outsider, disliked by the elites, looked down on, a TV star. And yet he became . . . Reagan.

I hear this a lot, mostly from idiots, but this time I engaged.

Look, Mr. Trump is not Ronald Reagan, I said. Reagan served two full terms as the governor of a state so vast that if it were a country it would have been one of the important economies in the world. He was a union president who served seven terms during the most fraught time in Hollywood’s history and emerged respected by all sides. He was no novice.

He was the leader of an entire political movement (however nascent) for more than a decade before taking the White House. Yes he had been an entertainer, an actor, and had loved it and seen himself as an artist. And it is true that he was looked down on by liberal elites. But it is not true that nobody respected him. The people elected him in landslides.

She moved her mouth in the way people do when they’re reminding themselves it isn’t polite to bite people in restaurants.

“Reagan wasn’t Reagan in 1980,” she explained.

“That is exactly who he was,” I said.

No, she replied: He hadn’t had his triumphs yet. People didn’t know he would go on to be who he was.

I said that they knew who he was based on his history and previous accomplishments which is why they felt free to make him president.

We went round and round, and in the end resolved nothing.

But what I thought for weeks afterward was: Trump supporters, please stop this. The man you back has never held office and has not proved himself as a leader of men. You have to include that in your arguments.

It is probably the case this year that most voters see the issue of character as null and void—neither candidate is admirable in that area. As for personality, I suppose it’s a matter of taste. But it must be noted that the most consequential decision of Reagan’s young presidency, when he fired the striking air-traffic controllers, was determined wholly by Reagan’s character—by his guts and willingness to gamble for what he was certain was right.

Trump supporters should be able to make an affirmative case for their candidate without diminishing Reagan or anyone else. You shouldn’t cut down a man you know was great to make him fit your candidate’s size. It is poor political etiquette. It’s also historical parallelism gone mad. Mr. Trump isn’t Reagan, and he isn’t Andrew Jackson either. He’s Mr. Trump. Take him on his terms and make the case.

You can say that the old standards have been swept away, that when it comes to character we’re a changed nation, that Mr. Trump and Hillary Clinton are the result of that decline, and that you pick from among the candidates on offer.
More Declarations

Hillary’s Gift and Britain’s Choice June 17, 2016
A Party Divided, and None Too Soon June 2, 2016
Clinton Embodies Washington’s Decadence May 27, 2016
Clinton-Sanders: Maybe That’s the Ticket May 19, 2016

You can argue, if you see it this way, that you detect in Mr. Trump a vein of old-fashioned America-loving patriotism. Maybe you suspect, or at least hope, that after a long career serving only himself—getting rich, chasing glamour—he wants to apply his last energies to serving the country that made him possible, and in which his children will live.

You can argue that Mr. Trump is the kind of electric figure who will give Washington a jolt—maybe he represents more current than the system can tolerate, maybe he’ll blow all the circuits, but maybe he’ll force a helpful reset of the grid.

You can say of Mr. Trump, as one of his supporters did, that the body politic is sick and he is the enema Washington needs.

You can argue that the Republican party was frozen by accepted wisdom and beholden to donors, but now, in a stroke, new thinking on immigration, trade and entitlement spending is ascendant. You can argue that Trump, just by showing up, has begun to break the policy logjam between the party and half its base. He has broken a brain-dead consensus.

You can argue what Franklin Roosevelt is said to have remarked when he appointed Joe Kennedy as first chairman of the Securities and Exchange Commission: that it takes a thief to catch a thief.

You can say, as a veteran Manhattan media leader, not known as a conservative, recently did, that Hillary will do nothing good but Donald might, if even by accident. He intends to vote for Mr. Trump, but adds: “It will all end in tears.”

You can begin a case, an argument, in all these areas.

But you can’t say that Mr. Trump is Ronald Reagan, because he is not, and you sound desperate and historically illiterate when you insist he is.

Stop trying to paint Reagan’s portrait into Mr. Trump.

Paint Mr. Trump.

*   *   *

I close with Trump cooties.

Donald Trump needs serious, substantive people to help with his campaign and advise him in foreign and domestic policy. But some will not join him because they don’t want to get Trump cooties. They don’t want the stigma of working with him.

Some are sincere—they don’t approve of him. But many fear having their careers associated with him and with what they expect will be his inevitable failure either in the White House or on the way there.

Those fears might be lessened if Mr. Trump took the moral advice offered by Hugh Hewitt this Thursday on his radio show. Mr. Hewitt told Mr. Trump to “rebuke the crazy one percent” who are Trump supporters but also anti-Semitic and racist.

Mr. Trump indicated that he understood and said he has rejected them “so strongly and so harshly.” He felt he hadn’t been given credit for this.

So we’ll go back to Reagan. When he was running for governor he was criticized after the John Birch Society, which had accused Dwight Eisenhower of being a communist, came out for him. Reagan said, as I recall, that the Birchers were buying his philosophy, not the other way around.

Clear enough and did the job.

Maybe if Trump wants to be compared to Reagan he should act more like him.