Former Florida Gov. Jeb Bush tussled with Republican presidential front-runner Donald TrumpDonald John TrumpMcCabe says he was fired because he 'opened a case against' Trump McCabe: Trump said 'I don't care, I believe Putin' when confronted with US intel on North Korea McCabe: Trump talked to me about his election victory during 'bizarre' job interview MORE Tuesday night, jumping to defend himself against Trump's insinuation that he isn't tough enough to serve as president.

“We need toughness, I think Jeb is a really nice person, but we need tough people, we need intelligence and we need toughness,” Trump said Tuesday during the CNN GOP debate.

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But Bush cut in and criticized Trump for stating two months ago that the fight against the Islamic State in Iraq and Syria (ISIS) was not America’s fight. When Trump tried to take control and ask who was talking, Bush declared: “I’m talking now.”

The exchange occurred right after Trump defended his call to kill family members of terrorists as a deterrent.

 “This is troubling,” Bush said of Trump’s idea.

“We are at war, they’ve declared war on us and we need to have a serious strategy to destroy ISIS. But the idea that that is a solution to this is just crazy.”

Bush, who has been criticized for a lack of fire during previous debate performances, has kept Trump square in his sights throughout the debate. In the first few minutes, he said Trump would be a “chaos president.”