Just when you think Donald Trump is truly brilliant. . .he does something to look pretty dim. On the upside, he totally humiliated Ted Cruz twice on Wednesday, first by “buzzing” Cruz’ speech to supporters during the day, then stomping on the end of Cruz speech at the convention, walking in, smiling and waving, while Cruz was still speaking. It was truly a work of art.

Related: Watch Donald Trump’s 2016 Convention Speech

But then, the day before giving his own acceptance speech, he went against every Republican since World War II. In fact, Dwight Eisenhower was spinning in his grave. The self-inflicted wound was Trump’s comment on NATO.

Donald Trump’s latest broadside against NATO, the military alliance that has long served as a pillar of Western unity, has further aggravated the disunity in the Republican Party as he prepares to accept its nomination for president.

In an interview with The New York Times, Trump said the United States shouldn’t automatically come to the defense of fellow NATO members if they are attacked unless those countries have paid their bills to the alliance. That approach flies in the face of one of NATO’s bedrock principles, Article 5, which requires NATO states to come to the aid of a fellow member under assault.

Someone should describe to Trump what a “treaty” is. And while they’re at it, they should explain what a “Republican” is. At a time when the party wants to criticize President Obama for not taking action over the Russian annexation of Crimea, he said just the wrong thing.

The comments drew scorn not only from American allies but also several top Republicans, undermining the party’s efforts to project unity during its national convention this week in Cleveland. They were published less than a day before Trump is due to deliver a major speech at the convention, and they further fueled the perception that Trump is a lackey for Russian President Vladimir Putin.

Mitt Romney, who was famously ridiculed for saying that the Russians are our main foreign threat, during the 2012 campaign, must be spinning in his Rolls Royce. . .

In the Times interview, Trump also said he would not chide authoritarian leaders for cracking down on civil liberties or their political rivals; that he’d pull the U.S. out of the North American Free Trade Agreement if Canada and Mexico didn’t agree to better terms; and that he may withdraw U.S. troops deployed around the world, even from sensitive areas such as the Korean peninsula.

But the Manhattan billionaire’s comments on NATO were unusually striking. Trump, who has often questioned whether other NATO states are carrying their share of the financial and military burdens that come with the alliance, said that if he became president the U.S. would only come to the assistance of a member state under attack if it “has fulfilled their obligations to us.”

Trump has been praised by many for his “sunset” way of looking at the world. That is, don’t take anything for granted; question every act, law, and relationship. But seeming to support Russia, while undermining both Eastern Europe and the NATO alliance, is probably not the thing to do before the convention is even over.

Oh, and besides all those other people, like Republicans, Trump’s comment did not go well with supporters of the military, either.

“Statements like these make the world more dangerous and the United States less safe,” Sen. Lindsey Graham, a South Carolina Republican and frequent Trump critic, said in a statement. “If Mr. Trump is serious about wanting to be commander-in-chief he needs to better understand the job which is to provide leadership for the United States and the free world. . .

“I’m 100 percent certain how Russian President Putin feels — he’s a very happy man,” Graham said of the Trump comments’ fallout.

Well, that’s ok. One misstep. Nobody’s perfect. It’s not like he alienated other Republicans on the day of his acceptance speech, right? Right?

Just hours before accepting the Republican Party’s presidential nomination, Donald Trump taunted his party on Thursday, ripping into his rivals and joking that, had he run as an independent, he could have defeated the GOP.

During a luncheon with 300 top donors just blocks from the convention center here, Trump said the Republican National Committee wanted him to sign a loyalty pledge last year because it was afraid he’d run as an independent and it knew he would beat the GOP’s candidates. POLITICO received a recording of portions of his remarks, and four sources in the room also described his comments.

After attacking the party, Trump went after individuals.

“Honestly, it could have been a career-ending thing, what he did,” Trump said of Cruz. “He got booed out. His Texas delegation was expecting him to and really thought he was going to endorse. Honestly, I don’t care.”

“They ran Ted Cruz out of the room!” he said. “There wasn’t a person in the room that liked him! … That’s unity!”

He also continued his assault on Ohio Gov. John Kasich, who has refused to endorse Trump or appear at this week’s convention, which is being held in Kasich’s home state. Trump’s and Kasich’s forces have spent much of the week attacking one another.

“If I got beaten as bad as Kasich got beaten by me, I wouldn’t support him either,” two people quoted Trump as saying. . .

Trump even teased former Texas Gov. Rick Perry, a former rival who was in the audience, about negative things he said about Trump during the campaign. . . “I’ll never forget one of the lines. … He said, ‘Donald Trump is a cancer on the Republican Party.’ I said, ‘Man! That’s bad!’ And that was one of the nicer things!”

It’s a year like no other. Trump breaks all the rules. But that’s not always a good thing.