The Republican contender who is gaining at the moment is former House Speaker Newt Gingrich, who leads the eight person nomination race in several national public opinion polls.

“I don’t claim to be the perfect candidate," said Gingrich. "I just claim to be a lot more conservative than Mitt Romney and a lot more electable than anybody else.”

Cain’s drop in the polls seems to have helped Gingrich, who has emerged as the main alternative to former Massachusetts Governor Mitt Romney.

Romney has long been considered the frontrunner in the Republican race, and he continues to focus most of his attention on President Barack Obama, as he did at a campaign stop in the Southern state of Florida.

“President Obama is a nice guy," said Romney. "But I don’t think he understands America. I don’t think he understands our economy. I don’t think he understands the power of free people, free to choose their course in life.”

Political strategist Matthew Dowd, an analyst for ABC News, sees the Republican race evolving into a two-man field.

“I think right now that anti-Romney vote is coalesced around the former speaker," said Dowd. "I think more of these votes go to Newt Gingrich, and I think Newt Gingrich is a force that Mitt Romney has to reckon with.”

Analyst Stuart Rothenberg, publisher of The Rothenberg Political Report, says Mitt Romney’s main challenge remains winning over Republican voters who doubt he is a true conservative.