Texas governor Rick Perry's first appearance in a Republican presidential debate confirmed his status as the early frontrunner in the race to challenge president Barack Obama.
Mr Perry and Mitt Romney have emerged as the two frontrunners. Sparring between the two of them last night dominated almost all of one hour 45 minute televised debate sponsored by NBC News.
The two men attacked each other's economic policies, health-care positions and qualifications to be president, offering contrasts in style and substance.
As the newcomer to the field, Mr Perry showed that he can deliver jabs and absorb them, as he became an early target for his competitors. "I kind of feel like the pinata here at the party," Mr Perry said.
The debate marked the start to a more aggressive phase in the primary campaign, with each man indicating he viewed the other as his major obstacle to the party's nomination.
"It's really a two-person race," said Republican consultant Scott Reed after the debate held at the Ronald Reagan Presidential Library in Simi Valley, California. "The rest of the folks were bystanders."
The contest between the two men is likely to set the tone for the fall campaign, as they each compete for voters, campaign funds and endorsements from party leaders.
Mr Romney and Mr Perry kicked off the debate by trading jabs over their job-creation records, citing each other's gubernatorial predecessors. The exchange revealed how each campaign has begun to target the other.
"Michael Dukakis created jobs three times faster than you did, Mitt," said Mr Perry, attacking Mr Romney's record as a former governor of Massachusetts.
Mr Romney fired back at the Texas governor with his own soundbite. "Well, as a matter of fact, George Bush and his predecessor created jobs at a faster rate than you did, governor," he said.
The two men largely ignored the six other Republican candidates on the stage at the library, which is the burial place of party icon Ronald Reagan.
The debate marked the first time the candidates had all shared a stage since Mr Perry announced his campaign on August 13th and overtook Mr Romney in public opinion polls. Mr Perry was supported by 27 per cent of self-identified Republicans while 22 per cent backed Romney in a Washington Post/ABC News poll taken between August 29th and September 1st.
Political pollsters caution that the race remains fluid, with few voters completely sold on any candidate.
In the Post/ABC survey, 34 per cent said they strongly supported their preferred candidate.
Sixty-six per cent categorized their support as "somewhat," indicating that they were still open to changing their preference.
The unsettled nature of the race could provide an opportunity for such candidates as Jon Huntsman, a former Utah governor and ex-ambassador to China for president Barack Obama, who has struggled to gain traction since announcing his campaign on June.
Mr Huntsman, who had promised to run a "civil" campaign, went on the offensive, criticising Mr Romney and Mr Perry for their health-care plans and economic policies as governors of Massachusetts and Texas.
Mr Huntsman delivered one of his sharpest rebukes to Mr Perry, who has questioned the science behind climate change and the role of humans in global warming.
"In order for the Republican Party to win, we can't run from science," said Mr Huntsman. "We can't run from mainstream conservative philosophy. We've got to win voters."
Even "Galileo got outvoted for a spell," Mr Perry responded. "Find out what the science truly is before you start putting the American economy in jeopardy."
Minnesota congresswoman Michele Bachmann, who leapt in the polls after a June debate performance and a victory in the Ames Straw Poll in Iowa in August, has seen her numbers drop since Mr Perry entered the race.
She struggled to break into the debate last night. Ms Bachmann and Mr Perry are competing for support from Tea Party activists and Christian conservatives.
"They overlap in their appeal," said Peter Brown, assistant director of the Quinnipiac University Polling Institute.
"There's a zero sum relationship between how Bachmann does and how Perry does." In the debate, Ms Bachmann attempted to remind the Tea Party activists who rallied around her candidacy in June about why they supported her.
"I've been leading on this issue for the last five years," said Ms Bachmann, when asked about cutting federal spending. "We have to have a president with a core sense of conviction that's going to fight on these issues."
Mr Perry used the debate to defend the fiscally conservative positions that have made him a darling of the Tea Party movement.
He reiterated his charge that social security is a "Ponzi scheme" that has failed Americans and isn't sustainable.
Former Bush political adviser Karl Rove and former vice president Dick Cheney are among leading Republicans who have denounced Perry's assertion.
Polling shows voters largely oppose cuts in entitlements like social security. Mr Romney was quick to tout his support for the program, eager to draw a sharp contrast with Mr Perry.
"Our nominee has to be someone who isn't committed to abolishing social security but who is committed to saving Social Security,"
Mr Romney said. "Under no circumstances would I ever say by any measure it's a failure."
Even as he squared off with Mr Perry, Mr Romney attempted to portray himself above the fray.
As his rivals attacked Mr Perry for issuing an executive order, rather than seeking legislation, to make Texas the first state to require schoolgirls to get vaccinated against HPV, a sexually transmitted virus, Mr Romney sounded magnanimous.
"My guess is that governor Perry would like to do it a different way second time through," he said. "We've each taken a mulligan or two."
Bloomberg