Donald Trump fired back at attacks from rival Jeb Bush on Monday, saying that he doesn't have "the persona" to go further in the race and can't even attack his opponents effectively.

"He thinks if he attacks me that's going to show he's tough but every time he attacks me he melts like butter," Trump said Monday on "CBS This Morning. "The last thing we need, frankly, is another Bush."

In the days leading up to the New Hampshire primary election, Trump has not spent as much time and energy on the other two leaders coming out of the Iowa caucus - Sens. Ted Cruz and Marco Rubio. He did clash with Bush several times during Saturday night's Republican debate and was all too happy to respond to Bush's attacks on the campaign trail. During a town hall in New Hampshire Sunday, Bush recalled Trump's remarks in July where he said Arizona Sen. John McCain was only a war hero because he was captured.

"Calling them losers - Donald Trump, you're the loser!" Bush said.

"Well just shows you how they lie. Number one I never called John McCain a loser," Trump said.

He did, in fact, use that term to refer to McCain during the July event, but it wasn't in the context of his military record. Trump said that he liked McCain less after his 2008 loss to then-Sen. Barack Obama, because "I don't like losers."

On "CBS This Morning," Trump concluded, "Jeb's a loser" because he has spent $100 million on his campaign but is "going nowhere."

Trump also weighed in on Rubio's debate performance Saturday where the Florida senator repeated the same attack line four times throughout the night. New Jersey Gov. Chris Christie slammed him for repeating the same "memorized 25-second speech that is exactly what his advisors gave him," But Trump wasn't quite as harsh.

"I said, 'wow, that is really strange,'" Trump said. "I didn't know he was going to be blowing up. It turned out to be a massive blowup but it was certainly different."

"It was, obviously, a sound bite that he likes, but you can use a sound bite once but you can't use it five times," he added.

He also admitted during the interview that he has more moments of self-reflection than his ultra-confident public persona would suggest when host Gayle King asked him if he ever wishes there is something he hadn't said.

"Well I do but I also don't dwell on the past," Trump said. "We all make mistakes and certain things you would have done differently in life, all of us, I mean who wouldn't have if we have the option but we never have that option. So you have to learn from life and if you do something, you don't do it again that's all."