During the interview, Scottie revealed the two things that really pissed him off with the Bush Administration. First, being set up to lie by Karl Rove and Scooter Libby. And second, learning that Bush had--himself--authorized the selective leaking of the NIE.

Scottie McC: But the other defining moment was in early April 2006, when I learned that the President had secretly declassified the National Intelligence Estimate on Iraq for the Vice President and Scooter Libby to anonymously disclose to reporters. And we had been out there talking about how seriously the President took the selective leaking of classified information. And here we were, learning that the President had authorized the very same thing we had criticized.

Viera: Did you talk to the President and say why are you doing this?

Scottie McC: Actually, I did. I talked about the conversation we had. I walked onto Air Force One, it was right after an event we had, it was down in the south, I believe it was North Carolina. And I walk onto Air Force One and a reporter had yelled a question to the President trying to ask him a question about this revelation that had come out during the legal proceedings. The revelation was that it was the President who had authorized, or, enable Scooter Libby to go out there and talk about this information. And I told the President that that's what the reporter was asking. He was saying that you, yourself, was the one that authorized the leaking of this information. And he said "yeah, I did." And I was kinda taken aback.

Here is the book passage.

The president was leaving an event in North Carolina, McClellan recalled, and as they walked to Air Force One a reporter yelled out a question: Had the president, who had repeatedly condemned the selective release of secret intelligence information, enabled Scooter Libby to leak classified information to The New York Times to bolster the administration's arguments for war?

McClellan took the question to the president, telling Bush: "He's saying you yourself were the one that authorized the leaking of this information."

"And he said, 'Yeah, I did.' And I was kind of taken aback," McClellan said.

"For me I came to the decision that at that point I needed to look for a way to move on, because it had undermined, I think, a lot of what we had said."

I would also not be surprised to see McClellan endorse Obama.  I believe Scott was once a Democrat back when his mother (who has since switched to republicans to indi) was Mayor of Austin.