On "The O'Reilly Factor" tonight, Bernie Goldberg revealed the one question he would ask Donald Trump at tomorrow's Fox News-Facebook Republican presidential debate.

Goldberg said he would ask the same question he previously asked Trump when he was doing a story for "Real Sports": "Mr. Trump, why do you brag so much?"

Goldberg revealed that Trump's answer to his question was, "I don't think it's bragging when you're telling the truth."

Goldberg pointed out that most successful grown-ups don't brag the way Trump does and explained that he wants to know what's going on in a candidate's head, not just what their policies are.

He also had some other advice he'd offer to anyone who's moderating a debate: check your biases at the door, politely interrupt and get a candidate to actually answer the question, point out if the question was not answered and never tell the audience how you feel about the subject.

Watch the "Factor" clip above.

Don't miss the Fox News-Facebook Republican presidential debate, Thursday August 6, live from Cleveland, Ohio at 8:50p ET, moderated by Megyn Kelly, Bret Baier and Chris Wallace. Plus, don't miss a live post-debate "Hannity" at 12a ET.

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