SPARTANBURG, SC -- Mitt Romney's campaign launched a barrage of attacks against Newt Gingrich just three days before South Carolina's primary amid signs the former House speaker could threaten Romney's bid for his third straight win in the primary cycle.

The former Massachusetts governor led his campaign in opening a fusillade against Gingrich, who's persisted at or near the top of the polls in tests of Saturday's first-in-the-South primary.

In a sign of how seriously his campaign is taking Gingrich as a threat, Romney broke from his usual form on the campaign trail -- which usually involves attacking only President Obama -- to instead deliver a rebuke of Gingrich's claims on his record on job creation.

"The speaker the other day at the debate was talking about how he created millions of jobs when he was working with the Reagan administration. Well, he'd been in Congress two years when Ronald Reagan came into office, " Romney said. "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."

Romney's words were just one part of an offensive that extended to his surrogates, who hosted a conference call and launched web videos questioning Gingrich's leadership abilities.

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The assault began earlier this morning with a web video released by the Romney campaign entitled "Undisciplined Leader," in which former New York Rep. Susan Molinari, who served with Gingrich in the 1990s, delivered the first blow.

"I served with Newt Gingrich in Congress. Newt Gingrich had a leadership style that can only be described as leadership by chaos,” Molinari said in the video. "I worry about the Republican Party’s chances to defeat President Obama if Newt Gingrich is the nominee."

On a conference call with reporters later in the morning, former Missouri Sen. Jim Talent, another Romney supporter, continued the attack, and warned that if Gingrich were to become the Republican nominee it would hurt the party.

"Each one of us [who served with Gingrich] has personal stories we can tell about going home and having to clean up after our speaker," Talent said. "It had an impact on the 1996 presidential election and, if he's the nominee, it will have an impact on the 2012 election and the impact's not going to be good for the conservative movement and the Republican Party."

If this all sounds familiar, it might be because the Romney campaign employed the exact same tactics following the first surge in the polls Gingrich had enjoyed in Iowa in early December. At that time, Talent and Former New Hampshire Gov. John H. Sununu lanced Gingrich for "off-the-cuff thinking" and "irrational behavior" on a similar conference call, with Sununu continuing to voice the attacks for days in interviews on television and in print.

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It now appears those attacks may continue. Today, the Romney campaign confirmed reports that Sununu will travel to South Carolina on Thursday to campaign for Romney.

This afternoon, the Gingrich campaign responded to Romney's comments on job creation.

""I fully expect the Romney campaign to be unendingly dirty and dishonest for the next 4 days because they are desperate, they thought they could buy this. They discovered that they can't buy this. I think they have internal polling that shows them loosing. I think they will do anything to try at any level and I need your help. People power will be money power. And I need your help," the candidate said at a town hall meeting.

"If your curious of what kind of leadership style Romney would use as president, today we are seeing what panic looks like," Gingrich spokesman R.C. Hammond told NBC News.

NBC'S Alex Moe contributed to this report.