The Republican candidates for president traded sharp blows over foreign policy and the future of the Supreme Court in an often unruly and chaotic debate.
After Iowa and New Hampshire, the race has now moved to South Carolina before the 20 February primary.
Front-runner Donald Trump repeatedly tangled with Texas Senator Ted Cruz and former Florida Governor Jeb Bush in a series of tense exchanges.
The lively audience repeatedly jeered and booed the candidates.
As the candidates shouted down and interrupted each other, CBS moderator John Dickerson warned: “We’re in danger of driving this into the dirt.”
Mr Trump and Mr Bush clashed over the war in Iraq and President George Bush’s role during the 11 September attacks.
Jeb Bush responded robustly to Mr Trump’s attacks, a departure for the former governor who originally sought a “joyful” campaign.
“We should have never been in Iraq,” Mr Trump said.
“They lied. They said there were weapons of mass destruction. There were none and they knew that there were none.”
