The fifth Republican presidential debate focused heavily on national security and terrorism on Tuesday in the wake of the deadly attacks in Paris and San Bernardino, California.
Former Florida Governor Jeb Bush took on front-runner businessman Donald Trump for his proposals in fighting against terrorist group DAESH.
"Donald is great at the one-liners, but he is a chaos candidate and he would be a chaos president," Bush said.
The debate came seven weeks ahead of the start of primary process in Iowa as Trump keeps his lead in the public opinion polls by a wide margin while other candidates struggle to gain popularity.
Trump, who pledged his commitment to Republican party after implying a possible independent run last week if he was not selected as the eventual nominee, reiterated his plan to ban Muslim from entering the US.
Despite worldwide criticism for his "hate-filled" rhetoric, Trump did not give in, insisting that US “needs toughness,” to overcome terrorism.
"Look, this is not a serious proposal. In fact, it will push the Muslim world, the Arab world, away from us at a time when we need to re-engage with them to be able to create a strategy to destroy ISIS," Bush criticised Trump.
On Tuesday, Trump has taken his anti-DAESH agenda to another step by proposing to kill the family members of DAESH terrorists.
Jeb Bush said this was "another example of [Trump's] lack of seriousness."
Bush, whose recent poll numbers have dropped to single digits was the more assertive in the debate.
“You're not going to be able to insult your way to the presidency,” he said to real-estate mogul Trump.
Trump on the other hand, defended his proposals including a plan shut down part of the Internet that DAESH used for recruiting members.
“I sure as hell don’t want to let people that want to kill us and kill our nation use our Internet,” he said.
Rest of the contenders mainly focused their criticism on President Barack Obama’s foreign policy.
Ted Cruz said weak foreign policy of the president in the war against DAESH is fueling the strength of the terrorist group.
"That would change when militants across the globe see that when you join ISIS [DAESH] you are giving up your life,” he said.
Ted Cruz and Marco Rubio disputed over Cruz’s proposal to “carpet-bomb” DAESH controlled areas in the Middle East.
Pointing out that Ted Cruz voted against defense authorization bills and had supported defense cuts, Rubio said "You can't carpet bomb ISIS [DAESH] if you don't have planes or bombs to attack them with."
The latest Reuters/Ipsos opinion poll shows Trump is the leading candidate with 33 percent of the votes and followed by Cruz with 15 percent.
Neurosurgeon Ben Carson is at 12 percent, while Rubio and Bush favorability rates are below ten percent.
The poll suggest Trump’s anti-Muslim rhetoric did not affect his leadership in the polls.