Newt Gingrich set his sights yesterday on Florida after a stunning win in South Carolina’s presidential primary, while main Republican rival Mitt Romney bowed to pressure to release his tax returns.

Mr Gingrich’s resounding victory Saturday turned the topsy-turvy race on its head, and his political resurrection ensures a dramatic 2012 battle to be the Republican standard-bearer against President Barack Obama on November 6.

It shattered the aura of invincibility cloaking the former Massachusetts governor and turned Florida’s January 31 primary into a pivotal contest that could either confirm Mr Gingrich’s momentum or restore Romney as the frontrunner.

Palm Beach County Republican Party chairman Sid Dinerstein said Florida was now the “make-or-break state” in the contest. “There is a very good chance therefore that after Florida the race is practically over,” he said.

“It was not a great week for me,” a stung Romney conceded to Fox News Sunday after watching his substantial lead in South Carolina evaporate in a matter of days – Mr Gingrich eventually won by a 12.5 percentage point margin.

The campaign rhetoric grew increasingly bitter as the multimillionaire investor Mr Romney and the pugnacious former House speaker locked horns.

There was “no question” he would go after his rival’s character more strongly than he has, Mr Romney said, implying he would call out Gingrich on his past ethics charges and his admitted marital affairs.