(Screenshot/Fox)
Donald Trump and former Florida Gov. Jeb Bush at the Fox Business Republican debate on January 14, 2016.

Republican presidential front-runner Donald Trump attacked former Florida Gov. Jeb Bush (R) during a conversation on tariffs during the Fox Business Network debate Thursday night, calling him weak.

Bush smirked and responded, simply: "Come on, man."

After commenting on the devaluation of the yen leading businesspeople to buy Japanese tractors rather than US-made Caterpillar tractors, Trump said it's "why we have to use our great businesspeople, and not political hacks, to negotiate with these countries."

Bush responded, citing Boeing and saying high tariffs would lead Japan to retaliate against the US and buy Airbus aircraft instead. (Airbus is a French company.)

"We need someone with a steady hand being president of the United States," Bush said.

Moderator Maria Bartiromo tried moving on, but Trump cut in and said that "we don't need a weak person being president of the United States because that's what we'd get if it were Jeb."

Bush looked incredulous and said, "Come on, man."

"We don't need that," Trump continued. "That's essentially what we have now, and we don't need that."

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