The Republican presidential candidates tore into each other as never before in their latest debate, aware that voting starts within 11 weeks and many votes remain up for grabs.
Mitt Romney emerged from the two-hour forum on Tuesday night as still the person to beat, but he was given a hard time over the issues of illegal immigration, healthcare and jobs.
The debate in Las Vegas marked the first time the contenders treated businessman Herman Cain as a serious threat, and they aggressively ripped apart his "9-9-9" tax plan.
Texas Governor Rick Perry criticising Mr Romney so vigorously that the two men seemed close to blows at times. Mr Perry was forceful from the start, battling to re-establish himself as the most viable alternative to the former Massachusetts governor.
Some exchanges were personal, almost petty. Mr Romney repeatedly chided Mr Perry and former Pennsylvania senator Rick Santorum for talking over him. Mr Perry accused Mr Romney of making false claims, and reminded voters that Mr Romney had employed illegal immigrants to do gardening work. Mr Romney said he had instructed the landscaping company to get rid of illegal workers.
Mr Perry said it was "the height of hypocrisy" for Mr Romney to criticise the Texan's immigration record. Mr Romney then put his hand on Mr Perry's shoulder and demanded: "Are you just going to keep talking?"