Sen.-elect Mitt Romney's remarks about President Trump in his recent new op-ed will "backfire" on him, Kentucky Sen. Rand Paul said Wednesday on "Your World."

Romney, the 2012 Republican nominee for president, said the president "has not risen to the mantle of the office."

He wrote that with such a "divided, resentful and angry" nation, Trump has seemingly lacked the leadership needed to resolve it.

Paul (R) said Wednesday that Romney's comments were "not productive" and that he'll receive backlash from conservatives.

"I think it's gonna backfire on him," he said to Neil Cavuto. "When you attack someone's character like that, I think that's such a low blow and so personally directed and so malevolent ... He's now called [Trump's] character 'dishonest.'"

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Paul said that although he had "choice words" about Trump during a presidential debate in 2015, he's since tried to avoid "personal characterization assassination."

"I have still voted against the president," he said. "Yet I choose not to go after and try to drum up a personal attack on him, which I think is just not useful."

He added that Romney is "petrified" that under Trump, the U.S. could end a war.

"I'm absolutely all-in with the president on this. If he can end a war, he'll be a hero that all the Independents will look at as well as some Democrats for finally being a president who ended war."

Paul said it "does nobody any good" to criticize the president's character for the entire country to see.

"In the end I think it's gonna look petty, and I think there's gonna be a backlash to this," he said.

Watch more of Sen. Paul's discussion on "Your World" above.

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