Ezra Klein has a piece on why “Donald Trump’s speech introducing Mike Pence showed why he shouldn’t be president.” It’s full of entertaining stuff about his introduction of Mike Pence, but it also explains why his performance matters.

Back in May, EJ Dionne wrote that the hardest thing about covering Donald Trump would be “staying shocked.” Watching him, day after day, week after week, month after month, the temptation would be to normalize his behavior, “to move Trump into the political mainstream.”

But today helped. Donald Trump’s introduction of Mike Pence was shocking. Forget the political mainstream. What happened today sat outside the mainstream for normal human behavior….

As with all things Trump, the speech was funny and magnetic. The guy is great TV. But it was also wrong. It was a blue stand-up set delivered at a board of directors meeting, a cruel roast offered at a child’s birthday party. Selecting and introducing a vice president is a heavy duty in American politics; it is the most power one person will ever have to potentially choose the leader of the free world. But Trump couldn’t see past himself to match the moment.