'His confidence is shaken': Longtime Trump-watcher reveals the moment he knew president was cracking

While President Donald Trump is in Argentina meeting with world leaders, cable news is busy discussing his state of mind after the revelation that his longtime personal attorney has flipped and admitted to lying about Trump's dealings with Russia.

On Friday night, MSNBC's Ari Melber hosted a panel that included Howard Fineman.

Fineman said he's "a pretty experienced Trump-watcher," having covered Trump as a businessman in New York and on the campaign trail in 2016.

"I think his confidence is shaken," Fineman said. "I thought that yesterday when I saw him on his way to the helicopter—giving one of the most confused and out-of-balance and unconfident answers I've seen him give."

Fineman said that Trump seems bothered by the fact that his children are possibly in the crosshairs of investigators is bothering him. Trump also seems weak now that he has allowed Mueller to cross the "red line" into an investigation of Trump's business dealings.

"What happens to a [con] man when he's out of confidence?" Melber asked.

"The more he talks about weak people around him, the more I think, in a way, to indulge in a little psychology, he's worried about how he's going to hold up," Fineman said. "The pressure of the presidency, in any circumstance, is almost more than anyone can bear. With this kind of scrutiny coming down, it's going to be interesting to see what he himself is made of."

Watch below.