Donald Trump idiosyncracy

CNN's Brian Stelter discusses President Trump's fitness for office and questions raised by Michael Wolff's controversial and disputed book "Fire and Fury." He says it is legitimate to ask about the president's fitness.

"This is now a global story," Stelter said about Trump's mental state. "One of Rupert Murdoch's papers in the UK ran a headline that said 'Trump's Mental Health Questioned By Top Aide.' The translation of that German headline [on screen] is 'Is Trump Still Sane?' Trump's answer, of course delivered on Twitter are that two of his greatest assets are his mental stability and being, like really smart. I got the sense Murdoch's 'New York Post' was kind of making fun of him this morning. Don't worry America! But many Americans are worried, and journalists need to cover that."

"It is not just the book that is forcing this fitness issue to the forefront," Stelter said, referring to Trump's tweets. "When the president of the U.S. threatens North Korea by invoking the size of his nuclear button, it is fair to question his fitness. Many reporters would conclude that he is not well."