How will Donald Trump do on the big stage at the Fox News Republican presidential debate this Thursday?

Fox News contributor Stephen Hayes said on "Hannity" tonight that Trump won't do well if he just lobs insults at his fellow candidates.

Hayes acknowledged that strategy might channel some frustration in the Republican base, but it won't be enough substance.

"If you call Jeb Bush a 'disaster,' you have to explain why Jeb Bush is a disaster," Hayes said.

Michelle Fields pointed out that Trump is not just blindly going after his fellow contenders, noting that he specifically criticized Bush for supporting Common Core.

"I think what people like about him is Donald Trump is willing to talk about issues that a lot of the Republicans don't want to," Fields said, citing immigration as a prime example.

She explained that people feel like Trump speaks from the heart.

"He needs policy proposals. He needs more substance. I think if he does that, he's going to be fine. He's a star."

Watch more above.

Don't miss the Fox News-Facebook Republican debate, Thursday Aug. 6, live from Cleveland at 8:50p ET, moderated by Megyn Kelly, Bret Baier and Chris Wallace.

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