WASHINGTON (AP) ― With businessman Herman Cain gone from the Republican presidential race, Newt Gingrich luxuriated in good polling news over the weekend ― two key surveys showing him well ahead of main challenger Mitt Romney in the fast-approaching Iowa caucuses.

Voters in the Midwestern state will vote in local caucus meetings on Jan. 3, the first-in-the-nation contests that choose delegates to the Republican national convention next September in Tampa, Florida, that will formally name President Barack Obama’s challenger in 2012.

An Iowa victory would mark a stunning turnaround for Gingrich’s once long-shot bid for the nomination. Most of his staff resigned in the summer as the former speaker of the House of Representatives was conducting a lackluster, minimalist campaign that placed him near the bottom in the eight-candidate race.

Gingrich began rising, however, as Cain was brought low by allegations of sexual harassment and a 13-year extramarital affair. To the last, Cain, the former CEO of the Godfather’s Pizza chain, denied any misconduct but ended his run Saturday, having slid from a brief period at the top of some polls into single-digit obscurity.

The wobbly U.S. economy remains the top issue in the 2012 election, and Obama is deeply vulnerable on that issue because unemployment, while down slightly, remains at a damaging 8.6 percent level and millions of Americans have lost their homes to mortgage foreclosures in the aftermath of the Great Recession that began in the waning months of George W. Bush’s presidency.

Polling shows Obama’s favorable rating at an all-time low, yet in head-to-head matchups with the leading Republican contenders the incumbent is either leading or in a statistical tie.

As the race narrows, Gingrich appears to have been the biggest beneficiary of Cain’s slide.

A Des Moines Register poll conducted Nov. 27-30 and released late Saturday found the former House speaker leading in Iowa among likely Republican caucus-goers with 25 percent support, ahead of the libertarian-leaning Texas Rep. Ron Paul at 18 percent and Romney at 16.

A separate NBC News/Marist poll showed Gingrich beating Romney, 26 percent to 18 percent, among likely Republican caucus attendees in Iowa.

While Gingrich has risen in Iowa, Romney, the former Massachusetts governor, still holds a sizable lead in surveys in New Hampshire, where he has a vacation home. The northeastern state holds the first primary election of the campaign season seven days after the Iowa caucuses. And the Obama campaign still appears to view Romney as the likely Republican nominee, given its continuing sharp attacks on what it says is his absence of a moral core politically.

Top Obama campaign adviser David Axelrod said on Sunday that Romney “seems to think that every day is a new day that he can simply change all of his positions, depending on what ― who his audience is or what the political circumstance is. And that is not what you want in a president of the United States.” He spoke on NBC television’s “Meet the Press.”

Romney ‘s record of changing positions on critical issues to meet the wants of audiences has been a huge drag on his campaign. In the past, when he was campaigning or holding office in Democratic-leaning Massachusetts, he took moderate to liberal stances on issues like abortion and climate change and was responsible for a reform of the Massachusetts health care system that became the model for one that Obama pushed through Congress.

Republicans, especially the most conservative among them, have vowed to repeal the law because they view it as a government takeover of the administration of health care. Those voters express a deep distrust of Romney’s conservative credentials.

Gingrich, himself, has a long record of shifting positions but so far that has not seemed to weigh down his extraordinary come-from-behind candidacy. Ironically, Gingrich, twice divorced and now married to a woman with whom he had an extramarital affair, has been the most obvious beneficiary of Cain’s precipitous slide. The former House speaker has successfully enticed many in the Republican tea party wing to his campaign and that backing could be further boosted as Cain’s deeply conservative supporters begin searching for a new candidate to back.

But some of the other candidates who sit well back in the race also express a belief that they can woo former Cain backers.

Paul and Rep. Michele Bachmann of Minnesota said Sunday they expected Cain supporters would fall in line behind them because of their messages on limited government, despite their low standing in the polls.

“A lot of Herman Cain supporters have been calling our office and they’ve been coming over to our side,” said Bachmann. “They saw Herman Cain as an outsider and I think they see that my voice would be the one that would be most reflective of his.”