Fox News contributor Trey Gowdy reacted to John Bolton's allegations in his upcoming book regarding President Trump's fitness for office by asking the former national security adviser: "If you really think he's unfit to be the leader of the free world, why didn't you say anything?"

"John Bolton's argument now is that Trump is unfit for office and should be removed, that he's committed high crimes and misdemeanors," Gowdy explained on "The Story."

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"Now, he had a chance to go before the House, he didn't do it. He had a chance to go before the Senate, he didn't do it. He had a chance to come on your or some other host's show and answer tough questions," he told host Martha MacCallum.

"But no, for $29.95, he's going to save you from this existential threat to our republic."

Bolton alleges in his upcoming 592-page memoir, due out next week, that Trump regularly gave "personal favors to dictators he liked," backed the idea of more concentration camps in China, and asked Chinese President Xi Jinping to help him in the 2020 election, according to excerpts obtained and published by several media outlets.

"I think people are smart enough to know if you really think he's unfit to be the leader of the free world, why didn't you say anything?" Gowdy said. "Why do I have to buy your book to get that?"

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Gowdy, a former chairman of the House Oversight Committee, also emphasized that Bolton has not testified to the allegations he makes in his book, "The Room Where it Happened."

"He ain't being cross-examined, he's sitting in his pajamas pecking away on his iPad," Gowdy said. "The power of cross-examination is you actually have to withstand the cauldron, withstand the heat of being questioned on it.

"Anybody can write a book and make assertions. Can you answer questions under cross-examination from the House or the Senate? Apparently he couldn't."

Fox News' Gregg Re contributed to this report.