In recent days, Donald Trump has slammed fellow Republican presidential candidate Marco Rubio on everything from his personal finances to sweating too much.

Marc Thiessen joined Megyn Kelly tonight to react to Trump's attacks on Rubio and what effect they might have on the Florida senator's 2016 campaign.

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Thiessen said he doesn't think Trump's attacks on Rubio will work as effectively as Trump's attacks on Jeb Bush.

"When he attacked Bush for being a 'low-energy guy,' it was devastating for two reasons," Thiessen explained. "One, because it rang true, and two, because it touched a nerve. Republicans are desperately afraid of having a low-energy nominee who is going to be like Mitt Romney."

He said that Rubio is not a low-energy or nervous candidate, despite Trump's attempts to link Rubio's nerves to his "personal perspiration habits."

As for Trump's salvo on Rubio's personal finances, Thiessen said that those claims were already adjudicated during the 2010 election, when one of Rubio's opponents, Charlie Crist, brought the same issues forth.

Thiessen said that Rubio is not a multi-millionaire and didn't get a "small" $1 million loan from his father to start his business career, as Trump did.

Megyn wondered if Trump will raise the same financial criticisms when he's face-to-face with Rubio at the Fox Business debate on Tuesday, November 10.

Watch more from "The Kelly File" above.

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