Each week of this campaign seems to bring a new, and usually appalling, way in which Donald Trump is completely unlike ordinary politicians. The latest is that he is not only willing but apparently eager to attack other politicians in his own party.

This tells us quite a bit about the campaign Trump running. But it also tells us quite a bit about the kind of president he’d be.

Here’s some of a report today from Jose DelReal and Jenna Johnson:

The intraparty skirmishing began with an attack on New Mexico Gov. Susana Martinez (R) during a campaign rally in Albuquerque, where Trump blamed her for mismanaging the state’s economy and suggested that she was shirking her responsibilities to her constituents.
“She’s got to do a better job. Okay? Your governor has got to do a better job,” Trump told a cheering audience Tuesday night. “She’s not doing the job. Hey! Maybe I’ll run for governor of New Mexico. I’ll get this place going. She’s not doing the job. We’ve got to get her moving. Come on: Let’s go, Governor.”
Next, at a campaign event Wednesday in Anaheim, Calif., Trump rattled off a string of attacks that played like a greatest-hits collection from the raucous GOP primary contest. He knocked South Carolina Gov. Nikki Haley’s decision to endorse Sen. Marco Rubio (R-Fla.), mocked former Florida governor Jeb Bush for his energy level and blasted 2012 ­Republican presidential nominee Mitt Romney as a “choker.” None of the three have endorsed him.
“Poor Mitt Romney. Poor Mitt. . . . I mean, I have a store that’s worth more money than he is,” Trump said, adding later: “He choked like a dog. . . . Once a choker, always a choker.” He also called Romney “stupid” and joked that he walked “like a penguin.”

Trump was probably angry at Martinez for not attending his rally and for private remarks she made a month ago that were critical of him. But it isn’t just people who haven’t gotten on the Trump train that he’s mad at. After Rick Perry declared his support for his party’s nominee, Trump mocked Perry at a rally, saying, “This politics is a dirty business. I have to tell you, I have never seen people able to pivot like politicians.”

In part, this is about the fact that Trump has a clear need not just to beat other people, but to assert his status over them, even to humiliate them. It’s why all his insults to his opponents have that that macho psychosexual element to them — he has to make sure everyone knows that he’s richer, he’s stronger, his wife is younger and hotter, he’s got bigger hands. And when they submit, it isn’t over. They have to keep being reminded that he’s the alpha male and they aren’t. That’s why he mocks Chris Christie, whose abject submission to Trump has been so pathetic, and that’s why he insults Perry even as Perry is endorsing him.

But there’s something else going on: Donald Trump simply cannot let go of a grudge.

This is something he freely admits. He is always on the lookout for someone treating him “unfairly,” which to him means any kind of criticism, disagreement, or, if it comes from the press, tough questioning. And as he said in January, “When people treat me unfairly, I don’t let them forget it.”

Remarkably, Trump seems to think this is an admirable quality, that his never-ending desire for revenge on those he thinks have wronged him is something we should admire. And it might be tempting to see his willingness to go after fellow Republicans as laudable candor. He doesn’t engage in the rote back-and-forth cross-party sniping we’re so used to — he criticizes everybody! But the thing about criticizing people from the other party is that it has a purpose. It’s meant to persuade people that your side is right and their side is wrong. But what’s the purpose of criticizing your own allies? There is none. It’s just about lashing out, personal pique, indulging your hurt feelings.

It certainly could present a problem in the general election by alienating Republican voters; Trump has gone after some of the party’s most popular figures, including not just Martinez and Romney (who is still admired by most Republicans) but also the likes of Scott Walker and Nikki Haley, if they weren’t eager enough to praise him. Summing up his philosophy, he says, “They talk badly, I talk badly, that’s how it works.”

What Donald Trump is doing on the campaign trail

U.S. Republican presidential nominee Donald Trump speaks at a campaign event at Trump Doral golf course in Miami, Florida, U.S. July 27, 2016. REUTERS/Carlo Allegri (Carlo Allegri/Reuters)

But is that how it ought to work? Let’s think about this in terms of the presidency. Trump’s personality has many ugly features, but it isn’t always clear what their implications are for the sort of president he’d be. For instance, Trump is obviously a misogynist who evaluates all women on the basis of their looks and youth. But beyond the kind of workplace he creates in the White House, that propensity could have limited effects. Would he work against equality in the workplace or reproductive rights? Sure, but so would any other Republican president.

Trump’s obsession with personal slights, however, could have profound policy consequences. He often says that eventually he’ll start acting “presidential,” yet from what we can tell, he believes that being presidential means nothing more than being polite. But being truly presidential means having the equanimity to take some attacks without striking back, particularly when it’s strategically advantageous either for yourself or the country. An effective president needs emotional control. He needs the ability to not get sidetracked by the attacks he’ll inevitably get, the ability to focus on what’s important and sometimes turn an opponent into an ally. Holding grudges is most definitely not presidential.

Just try to imagine if every time somebody criticized Barack Obama, he went off on a nasty tweetstorm berating the person, and spent time trying to think up sick burns he could use to make them feel small. Well that’s what Donald Trump does. And it plainly comes from somewhere deep inside him, which suggests that this personal vindictiveness and inability to let go of grudges wouldn’t just disappear once he became president. How would that affect his ability to shepherd complex legislation through Congress, or oversee fragile diplomatic negotiations, or deal with the inevitable crises every president faces?

Richard Nixon may have had an enemies list, but President Trump would have an enemies book, one that would never stop adding pages. This morning, Trump tweeted that “Such bad judgement and temperament cannot be allowed in the W.H.” Of course, he was talking about Hillary Clinton. But when he can’t stop himself from attacking even the people he needs to help him get elected, it raises more than a few questions about his own temperament.