Members of Congress, including House Speaker Nancy Pelosi, were reportedly on their way to the airport for a delegation to Europe and the Middle East when a message came from the White House: President Trump was canceling their trip. The bus carrying members for the flight to Brussels returned to Capitol Hill.

The move was widely and understandably seen as retribution by Trump for a letter Pelosi (D-Calif.) sent to him Wednesday suggesting his State of the Union address be postponed, given the ongoing government shutdown and the security demands of the elaborate plans that speech often entails. This was the ostensible rationale behind Trump’s move, too.

“In light of the 800,000 great American workers not receiving pay, I am sure that you would agree that postponing this public relations event is totally appropriate,” Trump wrote. He suggested that she not leave for a week, so that the shutdown might be resolved more quickly.

A spokesman for Pelosi quickly pointed out that the trip wasn’t going to be a week long and that, contrary to an assertion by Trump in the letter, there was no planned stop in Egypt.

But none of this was the point of Trump’s letter. He wasn’t concerned about Pelosi being gone for a week or where she was going. He wasn’t clipping her wings — the Democrats' collective wings — because he was worried about the shutdown. He did it for the same reason he’s done a lot of aggressive, unusual things that he’s done since declaring his candidacy in 2015.

He did it to throw a punch at his opponents.

Trump’s candidacy and his presidency are largely predicated on being the guy who picks the fights that commentators in conservative media say should be picked. The appeal of “owning the libs” — smacking down liberal political opponents or, more broadly, the elitists with whom the liberal population is believed to overlap — has enormous traction in some circles, including in much of Trump’s base. During the Republican primaries, he was the guy willing to bash George W. Bush. He was the guy willing to disparage Jeb Bush as out of touch. He was the guy willing to say the things about immigration that you would otherwise only hear from Laura Ingraham or on Breitbart News. His politics were born of that environment, born of immersion in Fox News in particular, and his political approach — unmoored by existing relationships on Capitol Hill — reflected it.

House Speaker Nancy Pelosi (D-Calif.) suggested President Trump postpone his Jan. 29 State of the Union address because of the partial government shutdown. (Blair Guild/The Washington Post)

It was an enormously helpful part of his general-election bid, too. His disparagements of Hillary Clinton were unusually nasty and virulent, the sorts of things that guys sitting on their couches would yell at the TV when Sean Hannity mentioned Clinton in a segment. Clinton’s wealth was suspect in a way that his own wasn’t because her wealth was the wealth of the elite snobs who believe in climate change and in telling you what to do. She, ironically, was seen as the wealthy establishment and Trump as the guy who made good in the lottery, despite those roles being largely reversed in reality. Clinton was the elite, the lib, and every time Trump threw a punch in her direction, few Republicans were going to object. Trump ran against Clinton in very personal terms and it worked. Republicans who didn’t really love him were reminded of how much they hated Clinton — and they pulled the lever for Trump.

Trump does things because they will annoy Democrats, and many people love it. His tweets of disparagement, however juvenile, are celebrated among many of his supporters. His Twitter reference to Rep. Adam B. Schiff (D-Calif.) in which he replaced the two F’s with two T’s? Hilarious. That Schiff was on that bus that got turned around Thursday was not lost on members of Trump’s base.

Obviously Trump’s letter to Pelosi was retributive. Obviously it was meant to frustrate her. But it is of a piece with his overall approach to his political opponents.

Consider the reaction of Erick Erickson, a conservative commentator whose relationship with Trump’s presidency has run more cold than hot. His reaction to Trump’s letter to Pelosi came in a blog post that consisted of a headline, a picture and three sentences. The headline was “This Letter From Trump to Pelosi May Be the Greatest Letter of His Presidency.” The third sentence was “His letter is hilarious.” The image was a large, laughing face.

This is how Trump does politics. He may not do everything that his base would wish, but he at least fights against the people they hate. That’s often good enough, as it was for Erickson on Thursday. It doesn’t mean that this is an effective strategy broadly or even an especially well-considered one. It doesn’t mean that he gained an advantage in the shutdown fight. But it does mean that, for some of his base and some Republicans more broadly, his letter was an appreciated move.

The New York Times' Patricia Mazzei spoke to people in Florida this month about the shutdown. She spoke to Crystal Minton, who had voted for Trump in 2016. Minton was now recovering from a hurricane and working without pay at a federal prison facility. She was understandably frustrated.

“I voted for him, and he’s the one who’s doing this,” she told Mazzei. “I thought he was going to do good things. He’s not hurting the people he needs to be hurting.”

The people he needs to be hurting, no doubt, are people like Pelosi.

President Trump's request for $5.7 billion toward the border wall has caused a nearly month-long partial government shutdown. (Patrick Martin, John Parks/The Washington Post)