Front-runner Donald Trump and former Florida Governor Jeb Bush traded sharp blows over foreign policy in the latest Republican presidential debate.
The candidates clashed over the war in Iraq and President George Bush’s role during the September 11th attacks.
The audience in the South Carolina debate hall repeatedly booed Mr Trump.
Jeb Bush aggressively answered Mr Trump’s attacks, a departure for the former governor who originally sought a “joyful” campaign.
The death of US Supreme Court Justice Antonin Scalia was addressed early on in the debate with all six candidates saying the next president should choose his replacement.
Texas Senator Ted Cruz said “we are one justice away” from the court reversing conservative legal gains.
Mr Trump said President Obama would probably pick a replacement, but stressed that the Senate should block him.
“Delay, Delay, Delay,” Mr Trump, the front-runner, said.