In the 2012 race for the White House, former U.S. House speaker Newt Gingrich is the latest Republican contender to surge in public-opinion polls.

Newt Gingrich is trying to capitalize on his newfound political momentum by running his first television ad in the Midwest state of Iowa, which kicks off the Republican nomination battle with its caucus voting on January 3.

"Working together we can and will rebuild the America we love," says Gingrich in a current campaign ad.

Gingrich has pulled ahead of former Massachusetts governor Mitt Romney in several national polls and in some important early voting states like Iowa and South Carolina. Just a month ago, Gingrich was mired in fifth place in Iowa.

Heading toward primaries

Romney continues to campaign hard in New Hampshire, which will hold the nation's first presidential primary on January 10, one week after the Iowa vote.

"And to bring America back to the principles that have always made us great is essential now, and that is why I think it is important for me to become the nominee, and hopefully I will be able to convince just enough people of that to become the next president of the United States," said Romney.

Romney still leads in New Hampshire, but polls show Gingrich is in second place and closing the gap.

The rise of Gingrich also comes on the heels of the decision by Georgia businessman Herman Cain to suspend his presidential campaign. Cain found himself consumed with responding to allegations he had an extramarital affair and that he had sexually harassed four women in the late 1990s, all of which he denied.

Benefitting from Cain's departure

Gingrich now stands to inherit some of that support, said ABC News Political Director Amy Walter.

"Newt Gingrich is most likely to benefit from Herman Cain's departure because he likes Newt Gingrich and he is likely to say good things about Newt Gingrich," said Walter.

Gingrich also can expect additional scrutiny to go along with his newfound momentum. Gingrich had a rough start to his campaign earlier this year, and some Republicans have reservations about his personal life and admissions of previous extramarital affairs.

Some of his rivals already are raising questions about his character, including former Pennsylvania senator Rick Santorum, who spoke on ABC's This Week program.

"I think they have to make a decision based upon the person's entire record, and certainly character counts," said Santorum.

Gingrich aims to maintain momentum

Gingrich hopes his newfound momentum will carry him to victory in the Iowa caucuses, just weeks away.

But political analyst Stuart Rothenberg said the Republican presidential race remains unpredictable.

"In polling now, Newt Gingrich seems to be leading the Republican race in many places. But we saw Michele Bachmann leading at a previous point, and Herman Cain leading, so the race is extremely fluid," he said.

Cain's decision to suspend his candidacy leaves seven active contenders for the Republican Party's presidential nomination, but some of them are expected to drop out if they do not perform well in the early voting tests in Iowa, New Hampshire, and South Carolina.