Here is a truth of life. When you act as if you’re insane, people are liable to think you’re insane. That’s what happened this week. People started to become convinced he was nuts, a total flake.

It was there in the polls. Fox News shows Mrs. Clinton with a 10-point lead, with Mr. Trump at 78% of the Republican vote, compared with Mitt Romney’s 93% in 2012. Mr. Romney won the white vote by 20 points; Mr. Trump is ahead by 10. “High-end Republicans are walking away,” says a GOP oppo guy. “Who is choking now?” The battleground states, too, have turned bad.

This is what became obvious, probably fatally so: Mr. Trump is not going to get serious about running for president. He does not have a second act, there are no hidden depths, there will be no “pivot.” It is not that he is willful or stubborn, though he may be, it’s that he doesn’t have the skill set needed now—discretion, carefulness, generosity, judgment. There’s a clueless quality about him. It’s not that he doesn’t get advice; it’s that he can’t hear advice, can’t process it or turn it into action.

“He’ll reach out, he’ll start to listen. He’ll change, soften.” No, he won’t. Nor will he start to understand that his blunders are a form of shown disrespect for his own supporters. They put themselves on the line for him, many at some cost. What he’s giving them in return is a strange, bush-league, pull-it-out-of-your-ear, always-indulge-your-emotions campaign. They deserve better.