The author of the book that reportedly has President Trump enraged and threatening legal action, defended his claims in ‘Fire and Fury’ as well as his own credibility to NBC’s Savannah Guthrie on Friday.

Michael Wolff, who was allowed access to Trump during the 2016 campaign and in the beginning of the official Trump presidency, said he operated like every other journalist and has recordings and notes to back up what is in the book.

Wolff reiterated and reconfirmed his claim that every person he spoke to, from low-level staffers to close advisers, question Trump’s fitness for office. He went even further this morning, saying Ivanka Trump and Jared Kushner, who are “in a deep legal quagmire” are blaming their troubles on Donald Trump’s poor decision-making.

On Trump questioning his credibility, Wolff said, “My credibility is being questioned by a man who has less credibility than perhaps anyone who has ever walked on Earth.” To be fair, there are more people than just Trump who question Wolff’s credibility.

But as many have said in the last week, even if half or 20 percent of what is in the book is true, it’s cause for concern.