Watch Trump, Bush fight like cat and mouse

Donald Trump and former Florida Gov. Jeb Bush sparred Tuesday night in the Las Vegas Republican debates. An abrasive Trump refused to back down on a policy position when Bush unexpectedly attacked the businessman for his rhetoric.

The fight started with a question from a college student about retaliation for terror attacks. Trump, the second-ranked candidate according to the Washington Examiner's presidential power rankings, told viewers he would punish the family members of terrorists who attack the U.S.

Bush immediately cut in, asking how killing the families of Islamic State members would help Americans.

"This is another example of the lack of seriousness. This is troubling because we're at war, they've decalred war on us and we need to have a serious strategy to destoroy ISIS, but the idea that that is a solution to this, it's just crazy, it makes no sense to suggest this," said Bush, ranked fifth. He also criticized Trump for getting his foreign policy experience from TV shows.