Washington Post reporter and A Very Stable Genius co-author Carol Leonnig said that friends of former Special Counsel Robert Mueller believe “something happened” to him over the course of the investigation into President Donald Trump, and that he’s “not the same man” they knew.

On Tuesday morning’s edition of CNN’s New Day, host John Berman quizzed Leonnig about the book, co-written by Philip Rucker, and a passage in which

“To me this is the first real account of from inside of the Mueller probe, and people who thought inside and outside looking in that Mueller might have dropped the ball here,” Berman said, and read a passage from the book in which the authors observe that Mueller looked shaky when delivering his report to Attorney General William Barr.

“Phil and I, my co-author, we are not medical professionals, but over and over again, John, we heard from people who are very close to Bob Mueller who found him a different person, a changed person, after two years of this investigation,” Leonnig told Berman.

“And they don’t know what that’s about,” she continued, but added “Some of them do and haven’t shared that with us.”

“But they know that something happened, he’s a different person, he was stumbling over his words, and you saw him in July in his testimony before Congress, there are people that I spoke to who are very very good family friends of his who said ‘I couldn’t watch the television anymore, I had to turn it off. It wasn’t the Bob I knew.’,” Leonnig said.

“And other critics who say at the end, he just wasn’t up to this modern era of political warfare, and may have got gamed out by the presidency,” Berman said.

“Many of our sources felt very strongly that Bob Mueller was playing a 1950s boy scout game, he was being an honorable icon and standard-bearer of the Department of Justice, whereas Bill Barr was playing in Trump’s 2000s and he was messaging this very well, he was the first person to get out the message: Donald Trump’s been exonerated,” Leonnig said.

Watch the clip above via CNN.

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