SPARTANBURG, S.C. - Mitt Romney's campaign on Wednesday deployed two former members of Congress who served with Newt Gingrich in the 1990s to hammer the former speaker for what they called his "unreliable" style of leadership.

"The speaker is running as a reliable conservative leader who can represent our movement and our party, and he's not that, because he's not reliable," said former Sen. Jim Talent (R-Mo.), who was in the House from 1993 to 2001, during a conference call with reporters.

"Yes, he can say exciting things," Talent said of Gingrich. "He also says things which undermine the conservative movement and he says them in outrageous and destructive ways."

As examples, Talent listed Gingrich's criticism of Rep. Paul Ryan's (R-Wis.) plan to reform Medicare, his opposition to President George W. Bush's 2007 troop "surge" in Iraq, his promotion of global warming legislation alongside former Speaker Nancy Pelosi (D-Calif.), and his attacks on Romney's past career in private equity.

Talent said Gingrich's own party removed him from his role as speaker in 1998 because "he had become the issue" and because members like him were tired of "going home and having to clean up after our speaker."

Former Rep. Susan Molinari (R-N.Y.), who participated in the call along with Talent, said Gingrich "does not have the personality and the temperament to lead a political party, to lead a movement against somebody like President Obama, and certainly to be commander-in-chief."

Talent and Molinari even blamed Gingrich for helping President Bill Clinton get reelected in 1996.

"The issue was no longer President Clinton, even during one of the more chaotic times in the White House," Molinari said, referring to Clinton's impeachment scandal. "The issue still remained the judgment and the words of Newt Gingrich."

Referring to the 2012 election, Molinari and Talent said if Gingrich were the Republican nominee, he would prevent the election from being a referendum on the incumbent Democratic president.

"We do not want Speaker Gingrich to help re-elect another Democratic president," Molinari said.

Molinari said Gingrich was "a very powerful negative force for the Republican Party " in 1998 and argued that "he has not changed and become more disciplined."

"The issue has to be President Obama's performance in office," she said, adding that if Gingrich is the Republican nominee, "we don't think that's a comparison that will be allowed to be made."

"If the speaker is the nominee he's going to be the issue," Talent added.

The Romney campaign also released two web videos featuring the Molinari and Talent Wednesday that echoed the same themes.

During a brief conversation with reporters on Wednesday, Newt Gingrich said the claims made in the ads were "stupid."

"Wait, wait, wait. They're saying I helped reelect a Democrat?" he said. "That's just stupid."

"Where do they get the gall to run this type of an ad?" he added later.

Gingrich said that during his time in Congress he fought with former Rep. Tip O'Neill and led the effort to defeat former Rep. Tom Foley, adding that he helped Republicans gain a majority in the House.

"My only question is what did Mitt Romney do? Who did he help elect? What was he doing during those years?" Gingrich said. "That's silly."

The Romney campaign's decision to schedule the call and release the web videos featuring Molinari and Talent are signs that they are worried that Gingrich is making a late surge here ahead of Saturday's primary, after his explosive and controversial debate performance on Monday night that energized the conservative audience in the debate hall.

The latest South Carolina poll, released on Tuesday by Monmouth University, showed Gingrich with 22 percent and Romney with 33 percent support in the state. Numbers released over the next day or two will reveal whether the former speaker is moving within striking distance of Romney.

Romney communications director Gail Gitcho brushed off a question about whether the Romney campaign is seeing Gingrich's numbers improving in its internal polling data.

Of the decision to hold the call, Gitcho said,"You can just chalk that up to us distinguishing ourselves, our campaign and our candidate from that of Speaker Gingrich."

WATCH the Romney campaign's videos featuring Molinari and Talent:

UPDATE: 1:30 p.m. -- Mitt Romney, in his first campaign event of the day here Wednesday, supplemented his campaign's overt criticisms of Newt Gingrich with more subtle jabs at the former House Speaker.

Nonetheless, Romney's focus on Gingrich in a brief speech on the campus of Wofford College signaled that his campaign sees Gingrich as its main threat ahead of Saturday's primary vote.

"One of the things I'm so proud about of our party is that we stand up for freedom, and for free enterprise. I was disappointed over the last couple of weeks to see one of my opponents attacking free enterprise just like the president was. That's not the role of the Republican Party. That makes us sad," Romney said.

"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," he continued. "Well, he'd been in Congress two years when Ronald Reagan came to office. 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 credit for helping create jobs is like Al Gore taking credit for creating the internet."

"This president's got it entirely wrong when he attacks the private sector. Don't attack the private sector. Don't attack risk-takers. Dont attack those that are trying to create a brighter future for themselves and their families. Don't attack profit. Profit, by the way, is what allows businesses to hire people and grow. Free enterprise is under attack from the right and from the left. We've got to stop it and stand up for American freedom everywhere we see it."

Elise Foley reported from Columbia, S.C.

CORRECTION: This article previously stated that Bill Clinton was re-elected in 1998, when he was in fact re-elected in 1996. The error has been corrected.