Donald J. Trump, the master brander, has never found quite the right selling point for his party’s health care plan.

Analyzing two years of his tweets highlights a pair of lessons about his messaging prowess that were equally on display as the Republican health care bill, weakly supported by even Republican voters, collapsed again in Congress on Monday. Mr. Trump is much better at branding enemies than policies. And he expends far more effort mocking targets than promoting items on his agenda.

Both patterns point to the limits of the president’s branding powers when it comes to waging policy fights. He hasn’t proved particularly adept at selling his party’s ideas — or shown much inclination to turn his Twitter megaphone toward them. He seemed effective in branding his immigration policy during the primary campaign — #BuildTheWall — but even that subject has occupied less of Mr. Trump’s attention on Twitter since he became president than, say, CNN.

By contrast, dating to the campaign, Mr. Trump has been deft at branding his opponents. There is no definitive canon of Mr. Trump’s messaging, but his Twitter feed serves as a reasonable proxy: It’s the social media account he’s best known for, and his use of it helped propel his candidacy. We’ve kept our tabulation of his Twitter insults current throughout his presidency. Using them as a guide – beginning in June 2015, when he declared his candidacy – you’ll notice patterns in how he refers to his political opponents.

Consider Hillary Clinton:

The word choice is memorable. But it’s also the repetition that’s important. In its simplicity and consistency, that message is textbook marketing, said William Cron, a professor of marketing at Texas Christian University. “This is what the product stands for,” he said (Mrs. Clinton being the product in this case). Marketing research also suggests that the more we’re exposed to a belief or a brand, the more likely we are to believe that others share or use it. And so by repeating the slogan, Mr. Trump also feeds the notion that Mrs. Clinton is widely believed to be crooked.

Psychologists have another term for what Mr. Trump does here that is so effective. He “essentializes” Mrs. Clinton and his other opponents, like Lyin’ Ted Cruz.

His use of this phrase implies a subtle but important distinction: It’s not merely that Mr. Cruz tells lies; rather, lying is essential to who Ted Cruz is.

Mrs. Clinton didn’t just commit a crime (in Mr. Trump’s telling); she’s crooked to the core.

Elizabeth Warren doesn’t simply espouse foolish ideas, in his argument; she can’t be taken seriously at all.

This is the important difference between using a descriptive verb (“Ted Cruz tells lies”) and a noun label (“Lyin’ Ted”). Such minor manipulations of language, psychological research shows, can convey much more deep-seated, stable and central characteristics about a subject. And these labels preclude other identities.

“Essentialism,” write the psychologists Gregory Walton and Mahzarin Banaji, “implies that a characteristic is inherent in the person (self or other) rather than the product of circumstance; that it is biological rather than social in origin; stable rather than unstable; and capable of great explanatory power rather than little.”

The only thing you need to know about Marco Rubio, according to Mr. Trump’s branding efforts, is that he lacks stature. And that’s a deeply embedded quality that the man can never change:

The tactic is also used against The New York Times, a favorite target of Mr. Trump’s derision:

And the news media at large. Trump’s brand evolved from describing the media as “dishonest” to labeling it “Fake News” after he became president. The latter label holds more power because it suggests that dishonesty is endemic to the news media’s identity.

But even as Mr. Trump has been focused and disciplined over time in tailoring messages around his opponents, he has seldom done the same for policies and legislation, though these would seem like the larger prize.

Mr. Trump has used a number of slights to make the case against Obamacare, which he has frequently labeled as a “total disaster” or “disastrous,” or with variations on the theme of death (it’s dead, dying, in a death spiral).

But the affirmative case for the Republican alternative? None of his language has stuck. When Mr. Trump has tried to brand his party’s health care reform efforts in a positive light, his messages have largely taken the form of unmemorable promises about “better” or “great” health care in the future:

If any word kept coming up — and this one’s not from his Twitter feed — it was his reference to the House bill as “mean.” The president repeatedly confused even Republican legislators over what form of health care law he favored (on Monday night, he came out, yet again, for the strategy he previously rebuffed of repealing the Affordable Care Act now and replacing it later).

In the past two years, he has tweeted about “tax reform,” the G.O.P.’s next major goal, only three times. “Big TAX REFORM AND TAX REDUCTION will be announced next Wednesday,” the president tweeted on April 22. When the following Wednesday rolled around — and the White House released a one-page outline of the plan — his Twitter account had nothing more to say about it.

Messages about his immigration restrictions, another defining policy effort, have been muddled by Twitter diatribes against the judges ruling on it and debates over whether the ban should be called a ban. Mr. Trump even undermined the case for his administration’s own proposal (with the courts and the public) by repeatedly calling it “watered down.” As with the “mean” House health care bill, it became unclear on Twitter whether Mr. Trump was advocating the policy at all.

The strategies that he has used against his foes — the repetition, the simplicity, the consistency, the essentializing — could just as easily be deployed to promote subjects as to deride them. That is, after all, what much of marketing does (and what a few positive Trump Twitter parody accounts have attempted to do).

But Mr. Trump for the most part hasn’t done that. He has used the tactic to promote himself: He is, above all, “a winner.” The endless repetition and emotional simplicity seemed to work during the campaign as he promoted the WALL (not a fence!). But now that he’s president, what if he cheered the Republican health plan as doggedly as he scorned “Crooked Hillary”? What if he devoted as much effort to defining the stakes of tax reform as he has spent branding his antagonists in the news media?