Donald J. Trump had a full day that began with a typically bizarre fit of petulance from the president of the United States.

Trump was set to meet with Russian President Vladimir Putin. They talked about Russian meddling with U.S. electoral processes; they announced a cease fire in parts of Syria; they agreed to move forward with bilateral relations.

Big stuff, right?

So what does the president tweet about this morning? He launched into a Twitter tirade against former Hillary Clinton campaign director John Podesta. Trump said “everybody” at the G20 summit he is attending is “talking about” Podesta and that ridiculous e-mail controversy that engulfed the Clinton campaign.

Everybody is talking about it? Every(bleeping)body, Mr. President?

I’m not going to dive into the details of what Trump tweeted. I do feel the need to wonder: What goes through the president’s mind when he is facing such a huge bilateral meeting? Can’t this guy focus on the issue of the day — which has done at all to do with Podesta, Hillary Clinton, or e-mails?

Podesta fired back. He called Trump a “whack job.”

I’ll just conclude that the president lacks anything approaching the kind of singular focus he needs to meet the huge challenges of the office he occupies.