Watch the full interview with Jeb Bush on "The Lead" with Jake Tapper at 4 p.m. ET
"Look, I don't get it. I don't see how over the long haul that you can insult your way to the nomination or the president -- certainly not the presidency -- and not the nomination either," Bush told CNN's Jake Tapper on "The Lead."
"This disparaging of women is deeply troubling. It just doesn't make any sense to me," Bush continued. "Carly Fiorina has made a good contribution already and will continue to make a contribution in this nomination process. She should be respected as a talented person and a viable candidate."
Earlier Thursday, Trump attempted to defend the remarks he made about his fellow GOP presidential contender in a Rolling Stone profile published Wednesday
"Look at that face!" Trump told a Rolling Stone reporter as Fiorina appeared on TV. "Would anyone vote for that? Can you imagine that, the face of our next president."
"I mean, she's a woman, and I'm not s'posedta say bad things, but really, folks, come on. Are we serious?" Trump said, according to the magazine.
Thursday that when he suggested Fiorina's face would make her unelectable, he wasn't talking about her looks.
"I'm not talking about looks. I'm talking about persona," Trump told CNN's Chris Cuomo on "New Day."
Bush also criticized the Iran nuclear agreement, saying Iran has no incentive to honor it.
"I think you need to look at the full relationship we had with Iran by giving them over $100 billion of revenue where they're going to be able to continue to be the largest sponsor of terrorism around the world," he said. "There's no evidence that they will comply with this agreement, because they've violated the agreements in the past."
Bush also said the U.S. needs to be more aggressive in its plan to help Syrian refugees.
"We've had a rich noble tradition of supporting refugees from all across the world," he said. "They've added vitality to our country. That's undeniable. We have a tradition of doing this and I think we have an obligation to do this in support of the displaced people that are suffering."
Asked about his newly unveiled tax plan, Bush said it would improve life for middle class Americans.
"We should have the lowest corporate tax rates in the industrial world, which I'm proposing. Eliminate the deductions and allow for investment to take place in our own country," he said. "The middle class in my proposal -- all of them -- will get, on average, a 33% cut in taxes. We need to boost people's spirits by giving them more money to be able to make decisions for themselves."
Despite his current place in the polls -- a new CNN/ORC poll
has him in third place with 9% support among Republicans -- Bush said he is "pretty confident" that he is going to be the Republican nominee.
"I think ultimately the three things that matter are you have to have a heart for people, you have to have ideas to lift them up and you have to have the leadership skills to make sure people know it's actually possible," he said. "I have those skills and I'm going to share them with passion and conviction."
Bush continued to tweak Trump on the campaign trail in Exeter, New Hampshire, Thursday night, telling reporters Fiorina and Ben Carson, with whom Trump has recently feuded, "have to get in line."
"I'm still the number one beneficiary of the Donald's insults. Look, he is who he is. He likes to disparage people," Bush said.