The “Late Show” host spotted a moment that says it all.

Stephen Colbert said Donald Trump delivered a “fun musical tribute to cognitive decline” at a town hall event this week when the former president cut off questions and then danced and swayed on stage for 40 minutes.

And the week only got stranger after that as Trump turned in a rambling and combative performance at the Chicago Economic Club.

“At the Chicago Economic Club, he acted like a guy who really woke up on the wrong side of dementia,” Colbert said, then rolled a clip of the moderator asking a question that involved Wall Street Journal economic projections.

Trump responded by attacking both the Journal and the moderator.

“And folks wonder why I don’t want to have that charmer back on my show,” Colbert said. “I’ve already had him on once.”

Colbert said in a PBS interview last month that he wouldn’t have Trump on his show again.

“I’ve had him before and he was kinda boring,” Colbert said. “So, no.”

That triggered Trump, who fired off an angry rant against Colbert on his Truth Social website.

Colbert later admitted that he used the word “boring” because he knew it would set Trump off.

“He’s clearly upset because I called him boring, and I called him boring because I knew it would upset him,” Colbert explained. “Which it did, because he’s so predictable, which is ultimately what makes him: kind of boring.”

Colbert on Tuesday night tried to picture what would happen if Trump did come on the show and took part in his long-running “Colbert Questionert” segment, which involves a series of questions from the silly to the profound.

“What happens when we die?” Colbert said in his Trump voice. “I don’t die, you all die. I’m the only one who’s real.”