Republican presidential candidate and former Florida Gov. Jeb Bush called rival Donald Trump a “chaos candidate” during CNN’s primetime debate Tuesday.

Bush criticized Trump’s proposed ban on Muslims entering the U.S. and argued that the country needs to work with those in the Muslim community to fight against the Islamic State terror group.

“This is not a serious proposal,” Bush said. “Donald, you know, has been great at the one liners. But he’s a chaos candidate and he’d be a chaos presidency.”

Trump jabbed back at Bush and said the former governor was criticizing him just because he was running a failed campaign.