The debate turned contentious early on when the two front runners, Texas Gov. Rick Perry and former Massachusetts Gov. Mitt Romney, clashed over Social Security.
"This is a broken system," Perry said. "This has been called a Ponzi scheme by many people before me."
"But the question is, do you still believe that Social Security should be ended as a federal program as you did six months ago?" Romney replied.
"I think we need to have a conversation," Perry said.
"We're having that right now governor we're running for president," Romney shot back.
It was a make or break night for Minnesota Rep. Michele Bachmann, who has lost momentum since winning the Iowa straw polls. She also took aim at Perry over his executive order on the HPV vaccine in Texas.
"To have innocent little 12-year-old girls be forced to have a government injection through an executive order is just flat out wrong. That should never be done," she said.
On the issue of jobs, Perry touted his own record as governor.
"Texas has during my period as governor created over a million jobs," he said.
But Ron Paul quickly fired back, saying 170,000 jobs were government jobs.
The candidates did agree on the need to get government spending under control and the economy back on track.
Before the debate, Romney won the endorsement of former Minnesota Gov. Tim Pawlenty.
But in GOP polls, Romney is still behind Perry, who won the endorsement of Louisana Gov. Bobby Jindal.