Martha MacCallum appeared to catch former Defense Secretary James Mattis off guard Wednesday with a question about running for office.

The Marine General, who sat down with the Fox News host for an interview, hesitated briefly before delivering his response — and MacCallum noticed immediately. (RELATED: Mattis Retires From Trump Administration)

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MacCallum noted that Mattis, an avid reader, had a 7,000 volume collection. He responded by explaining just how much young Marines were expected to read.

“Yeah. The Marine Corps assigned you a reading list when you first come in the Marine Corps and when you get promoted, Martha, they give you a new list each time,” Mattis began. “You finally get all the books done when you are a captain and when they promote you to major, you gotta start over. Even generals, by the way, get a new list of books they have to read. The Marine Corps is not there to listen to you whine about your mid-life crisis. You read the books or else.”

“You got to read because if you don’t read, I don’t think you can lead effectively because you are learning and your troops are learning always at your mistakes,” Mattis added.

MacCallum changed the subject abruptly, saying, “A lot of people want you to run for president. What do you say to that?”

“I think we have a lot of great people in America, and I think that 40 odd years of serving the country in the military and in the defense establishment, I am eager to see the fresh ideas on people who handle a much broader array of issues that I have,” Mattis demurred.

MacCallum pressed, “So that’s a no?”

“Well, ah, that’s a no,” Mattis confirmed.

“A little hesitation,” MacCallum smiled.

“There is not a hesitation,” Mattis clarified. “I’m just trying to think how to say no even stronger.”