The moderate defends his status as favorite in the race Republican in the White House before the primaries in Mississippi and Alabama on Tuesday, two states "Old South" where rivals and of an election promise tighter.
The former governor of Massachusetts (northeast) is leading the race, after winning about 40% of the 1,144 delegates needed to win nomination of the party and become the enemy of outgoing President Barack Obama for president of 6 in November.
Face to Mr. Romney, MM. Gingrich and Santorum are trying to win each as the sole guarantor of the ultra-conservative values. But their duel divides the electorate to the right in favor of Mr. Romney.
Newt Gingrich, former Speaker of the House of Representatives, Southern man, will try to convince two wins to snatch it considers "mandatory".
Monday campaigning in both states are highly dependent on the oil industry, Mr. Gingrich touted his energy plan. "We need a U.S. policy that assures our energy independence from the Middle East so that no American president does not bow before the king most of Arabia", he said.
For his part, Mr. Romney - who announced in recent days a variety of supports to local elected officials in Mississippi and Alabama - has tried to charm the voters by greeting them in the manner of Southerners:"Hello y'all," he said.
Rick Santorum, for his part received the support of the conservative Duggar family with 19 children, who are the heroes of a popular television series.
The three men, who have campaigned tirelessly in the "Old South", are in a pocket handkerchief in Mississippi and Alabama.
In Mississippi, Newt Gingrich (33%) leads by a short head in front of Mitt Romney (31%) and Rick Santorum (27%), according to a poll published Sunday by the Institute PPP. But a Rasmussen poll last week Mr. Romney in the lead up.
In Alabama, according to an average of several polls conducted by the website RealClearPolitics, Mr. Gingrich is leading with 27% of the vote followed closely by Mitt Romney (26.3%) and Rick Santorum (25%).
Meanwhile, nationally, the battle is not over yet for Mitt Romney who is not certain to reach reach the magic number of 1,144 delegates. In a survey CBS / New York Times published Monday, Republican voters give the advantage to Rick Santorum (34%) against 30% for Mitt Romney. Newt Gingrich gets 13% and the Conservative isolationist 8%. But 73% expect to see moderate prevail.
So far, Romney has won 17 of the 26 states or territories overseas which have already held their consultations against seven for Rick Santorum, Newt Gingrich and two for no for Ron Paul.
Mr. Romney also garnered 455 delegates, against 199 for Mr. Santorum, Newt Gingrich and 117 to 64 for Mr. Paul.
Faced with a battle that drags Republican side, supporters of Democratic President Barack Obama welcome. But they too face their own difficulties.According to a poll published Sunday, the popularity of President Obama has fallen below 50% due to higher fuel prices.
A "caucus" meeting of electors, will also take place Tuesday in Hawaii (Pacific). Given the stakes in the South, Mr. Romney has delegated his son Matt. And Rick Santorum, his daughter Elizabeth.