Syndicated columnist and Fox News contributor Charles Krauthammer said Thursday on “Special Report with Bret Baier” that Republican presidential nominee Donald Trump’s central weakness is his vanity.

“I don't know why everybody's surprised of his lack of discipline. I mean he's been out there for 15 months, he's completely undisciplined,” Krauthammer said. “Yet, for about a month he's been led around, shackled, handcuffed by his staff, made to read from the teleprompter.”

Krauthammer added that it's not that simple for the Trump campaign to keep him under control.

“The minute you let him loose, meaning on the debate stage, where there is no prompter, and then immediately after when he's reacting... What emerges is his central weakness: Vanity," he said.