What did Donald Trump do today?

He blamed the press for the answers he gave to their questions.

Trump departs for the UK on Monday. He's spent this weekend making sure all eyes will be on him when he goes, by setting off a few different diplomatic bombs.

This morning, for instance, Trump insisted that he never called Meghan Markle (wife of Prince Harry) "nasty." There is, of course, audiotape of him saying it in an interview released Friday, which his own campaign helpfully tweeted out. 

But more substantially, Trump chose the week before his trip to visit outgoing Prime Minister Theresa May to weigh in on who should be her successor. In the same interview with The Sun where he called Markle "nasty," Trump threw his support behind Boris Johnson, because Johnson "had always been very positive about me."

May's replacement will be chosen by members of her own party, but Trump's public endorsement of one candidate in particular offended more or less the entire British political spectrum. It's pretty much unheard of for allies like the United States and the UK to have their heads of state interfere in one another's elections. (Hostile countries doing so is a different matter.) 

Asked today why he had done this, Trump blamed the media for reporting what he'd said.

Q: Mr. President, is it appropriate for you to be weighing in on Brexit and the Prime Minister -- who should be the next Prime Minister? 

TRUMP: Well, people ask me questions — like you; you're asking me a question. Don't ask me the question if you don't want me to talk about it.

The interviewer for The Sun did not ask Trump who he thought should be Prime Minister.

It's not the first time Trump has tried to tell Brits how to govern their country. Shortly after taking office, he lobbied to get Nigel Farage, a political supporter of his, appointed as Britain's ambassador to the United States. (The position was not vacant.) Trump seemed unable to understand that any British ambassador would be serving British interests, not his own.

Why does this matter?

• Lying about things a billion people heard you say on audiotape is less about lying and more about insulting your audience.

• The president, not the press, is responsible for the words that come out of the president's mouth.

• The relationship between the United States and its closest ally is too important to screw up this badly.