ROCK HILL Amid signs that the S.C. Republican primary race is tightening, front-runner Mitt Romney charged Wednesday at Winthrop University that Newt Gingrich is following President Barack Obama's lead in trying to sow class warfare and "replace ambition with envy."

Romney's campaign, as part of a one-two punch, also released two Web ads featuring former congressional colleagues of Gingrich describing his reign as House speaker as "leadership by chaos."

At the Rock Hill rally, which drew several hundred supporters, the former Massachusetts governor offered a full-throated defense of the free-enterprise system that has made him wealthy. He also took a brief detour from his usual attacks on Obama's record to criticize some of his surviving GOP rivals - especially Gingrich, who appears to be moving up in the polls after a Monday night debate performance that got rave reviews from Rush Limbaugh and Sarah Palin.

Gingrich and Texas Gov. Rick Perry have blasted Romney for presiding over job losses, including in South Carolina, during his tenure as head of Bain Capital, a private equity firm. In recent days, they've also called on him to release his federal tax returns.

"I've been disappointed that, even in our (GOP) race, that some Republicans have jumped on (Obama's anti-capitalism) bandwagon," Romney said. "My goodness, I listened to Speaker Gingrich the other night (criticize) some of the enterprises I've been involved in. I'm proud that I've been involved in the private sector."

A more subtle jab at the thrice-married Gingrich: Romney gushed on stage about his wife, Ann, who stood next to him. "I think I met her in elementary school ... but I really noticed her at 16," he told the crowd. "We've been going steady ever since."

Earlier, in Spartanburg, Romney belittled Gingrich's boast of helping create jobs during the Reagan administration.

"He had been in Congress two years when Ronald Reagan came to office," Romney said of Gingrich. "That'd be like saying 435 congressmen were all responsible for those jobs. Government doesn't create jobs. It's the private sector that creates jobs. Congressmen taking responsibility or taking credit for helping create jobs is like Al Gore taking credit for the Internet."

In addition to appearing in the new Romney Web ads, two former House members told reporters that Gingrich was an erratic leader who made it hard to govern and who invited a backlash from voters that helped Democratic President Bill Clinton win re-election in 1996.

"I can only describe his (Gingrich's) style as leadership by chaos," former Rep. Susan Molinari, R-N.Y., said in a call to reporters set up by Romney's campaign. "We do not want Speaker Gingrich to help elect another Democratic president."

Gingrich, sensing a tide turning his way just days before the pivotal first-in-the South primary on Saturday, warned voters to be on guard against smears from a suddenly worried Romney. "They're desperate," he said.

A new CNN poll released Wednesday showed Romney with the support of 33 percent of likely voters, Gingrich with 23 percent, former Pennsylvania Sen. Rick Santorum with 19 percent, Rep. Ron Paul of Texas with 13 percent, and Texas Gov. Rick Perry with 6 percent.

The four-night survey included only one night of calls after the Monday debate. Nonetheless, it showed Romney's lead dropping.

Karen Kedrowski, chair of Winthrop's political science department, said she wasn't surprised that the race is tightening.

"When I saw those earlier polls that had Romney ahead 20 points, I knew that was not going to stay and that his support was pretty soft," she told the Observer. "Romney has four other candidates trying to poke holes in his armor and that's going to undermine some of his support."

At the Rock Hill rally, Romney said his experience as a business executive put him in a position to turn the economy around - including in South Carolina, where the unemployment rate is almost 10 percent.

"I understand how jobs work, how they come and how they go," he said.

Four years ago, in the 2008 S.C. primary, Romney came in fourth in the state - and in York County.

In York, he polled only 11 percent, way behind county winner Mike Huckabee's 36 percent.

But S.C. Rep. Ralph Norman, who represents York, predicted he could carry York on Saturday on the strength of his electability.

"We got to win in November and get rid of Obama," said Norman, who has endorsed Romney now that his first choice, Herman Cain, has left the race.

Still, Norman acknowledged that Romney is in for a fight in the next few days. The race is "fluid," he said.

The candidates face each other again at 8 tonight in a debate televised nationally on CNN.

One issue that's likely to come up is Romney's taxes. He made no mention of them in Rock Hill, but he acknowledged this week that he paid a rate of around 15 percent on his investment income. That's a lower rate than what most Americans, who live off their salaries, pay.

Norman said Romney will have to address the tax issue soon.

"I'm glad it's coming up now" rather than in the heat of the fall campaign, the GOP state legislator said.

Romney hopes to make it three wins in a row Saturday with a victory in South Carolina. Though it's more conservative than Iowa or New Hampshire, the first two states to vote this year, it has long been a firewall for front-runners and, since 1980, every winner of the S.C. Republican primary has gone on to get the party's nomination for president.

Romney's strategy was summed up in the song - "Another One Bites the Dust" - that was piped over the speakers as the crowd waited.

Michele Bachman dropped out after Iowa, and Jon Huntsman bailed after New Hampshire.

The McClatchy Washington Bureau and staff writer Jim Morrill contributed.