For now at least, he left the criticism to Talent and former New Hampshire Gov. John Sununu, who held a conference call with reporters as the day began to dissect Gingrich's statements about Republican Rep. Paul Ryan's budget proposal this year.
Earlier this year, Gingrich's critique of Ryan's plan as "right-wing social engineering" and "imposing radical change" was roundly criticized by Republicans. And Sununu said Gingrich's response illustrates a habit of off-the-cuff speaking and thinking that raises a larger question of fitness to lead
"What he did to Paul Ryan is a perfect example of irrational behavior that you do not want in the commander in chief," said Sununu, a prominent Republican in Romney's must-win state of New Hampshire who served as chief of staff for President George H. W. Bush.
Added Talent: "Speaker Gingrich says interesting and insightful things. He also says outrageous things that come from nowhere, and he has a tendency to say them at a time when they most undermine the conservative agenda."
Meanwhile, Romney's team rolled out a series of emailed memos casting Gingrich as a turncoat Republican on Ryan's plan, which is popular with conservatives. One was titled: "With friends like Newt, who needs the left?"
And Romney's campaign also distributed talking points to allies on Capitol Hill in Washington that indicated the campaign plans to swipe at Gingrich's economic record by arguing that he doesn't have a background in the "real economy." Among the points: "Gingrich creates theories, Mitt creates jobs" and "Gingrich has spent a lifetime operating in theory, while Mitt has succeeded in practice."
Over the past few days, Romney has foreshadowed the attacks by drawing not-so-subtle distinctions with Gingrich, particularly on personal issues.
He started running a TV ad on Wednesday that promoted Romney's stable family life — and stoked questions about Gingrich's motivation to run and temperament to lead. Romney's allies did the same, with Talent and Sununu describing Gingrich, with whom both men worked over the years, as untrustworthy and self-centered.
They also warned that Gingrich's long history as an outspoken antagonist would play into the Obama campaign's hands, were he to be the Republican nominee. Talent, who served under Gingrich in the House in the 1990s, said he was not referring to the House ethics scandal that drove him from the speakership nor his two divorces and extramarital affair.
"If the nominee is Newt Gingrich, then the election is going to be about the Republican nominee, which is exactly what the Democrats want," Talent said.
The campaign also signaled that it won't overtly attack Gingrich's personal problems but will draw contrasts with his rocky personal life nonetheless by pointing out Romney's stable family life — especially in Iowa.
Ann Romney will be in the spotlight in Iowa in the coming days, accompanying her husband during the Friday stop in Cedar Rapids and then hosting an afternoon reception in West Des Moines. She'll also attend an event at Romney's Des Moines headquarters on Saturday ahead of the debate.
Subtlety on the personal front may be a smart strategy for Romney.
"He's got high negatives anyway. If he goes on the attack on personal issues, in Iowa, his negatives go up further," said Doug Gross, who was Romney's Iowa campaign chairman four years ago. "It polarizes him further."
Still, he added, Romney's effort to portray himself as more conservative than Gingrich on budget issues could hurt the former Massachusetts governor among the moderates who could help him beat expectations in the Jan. 3 caucuses. And, Gross said, Romney's revival of the Ryan plan also may annoy some House Republicans who supported it last spring but have been trying all year to soothe worried constituents about proposed changes to the prized health care safety net for older Americans in light of Democratic attacks.
Still, Romney's attack on Gingrich's ability to be president may resonate with Iowans.
A recent Washington Post-ABC News Poll in Iowa shows 43 percent of likely caucusgoers said Gingrich "has the best experience to be president," compared to 16 percent for Romney. They also trusted Gingrich more than Romney by big margins on handling the economy and immigration. Still, Romney is not viewed all that strong on these factors, so he's leaving himself vulnerable to attack, should Gingrich drop his positive pledge.
Less than a month before the Iowa caucuses, Gingrich is running ahead of Romney in polls in Iowa.
Romney now faces a dilemma: try to stop Gingrich with a full-throttle campaign in Iowa and risk falling short ahead of must-win New Hampshire or tentatively engage Gingrich in Iowa and risk allowing him to gain momentum heading into the first-in-the-nation primary Jan. 10.
Shannon McCaffrey in Greenville, S.C., contributed to this report.
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