“A weeklong blitz of negative ads from Ron Paul and ‘Restore Our Future,’ the pro-Mitt Romney super PAC, have taken a toll on Newt Gingrich’s standing in Iowa, internal numbers from the Rick Perry and Romney camps show, according to multiple sources.

“Sources didn’t provide specific numbers on how far he’s slipped, but it’s perceptible in both camps’ numbers, the sources said.

“Perry has been inching up, the sources said – in part thanks to his faith-based push but largely because of his controversial anti-gay rights ad, and the big question is whether he draws at all from Romney and pushes him down out of the top three finishers in the state…

“‘Gingrich [is] leveling off and the attacks are starting to permeate the minds of Iowa caucus-goers,’ said one veteran Republican caucus-watcher in Iowa.”

“There are indications — early indications — that is happening now, with the Iowa caucuses less than three weeks away. ‘I don’t know if I’d call it slippage yet, but there’s no doubt, I think, people are pausing now,’ says influential Iowa social conservative leader Bob vander Plaats. ‘I’m sensing a pause. I’d call it a due-diligence pause. I think a Ron Paul commercial that is blistering Gingrich has had an impact, where people are at least going to pause.’…

“‘People are saying OK, let’s reassess this,’ the insider continues. ‘Is this really a decision we want to make? What I’m hearing is thinking about the general election and the unpredictable nature of him as our nominee. I don’t have any empirical data to back it up, but it’s just a feeling I’ve gotten in the last 24 hours.’

“‘I think it’s happening,’ says a third uncommitted Iowa politico. ‘His support has definitely stopped going up and is probably going down.'”

“Since Gallup began Daily tracking of national Republican nomination preferences last week, Gingrich has averaged a 12-point advantage over Romney, with a high of 15 points in Gallup’s initial report based on Dec. 1-5 interviewing. The current 9-point tracking lead for Gingrich is the smallest yet for the former speaker of the House.

“Gingrich has come under increasing attack from his rivals in debates, on the campaign trail, and in television ads since he became the front-runner this month, which may be chipping away at his support, now at 31% after being 37% in the initial tracking report.”

“The poll found that if the November 2012 presidential election were held today, Obama would defeat Gingrich, 51 percent to 38 percent. By contrast, Obama would defeat Romney by a narrower margin, 48 percent to 40 percent.

“Analysts say the results reflect the risk that Republicans could face if they nominate Gingrich, whose strong performances in debates have won him support among conservatives seeking an alternative to Romney…

“‘This is the Republican dilemma,’ said Calvin Jillson, a political science professor at Southern Methodist University. ”Do I want to enjoy myself by voting for Gingrich … or do I want to look toward the general election and see a winnable contest?'”

“Gingrich is further underwater, with an unfavorable rating that’s essentially the same as Obama’s — 48 percent — but a favorable score that’s 13 points lower, 35 percent. (More are undecided about Gingrich than about the president.) Moreover, while just 23 percent see Obama ‘strongly’ favorably, Gingrich’s core group of strong supporters is just half as large, 12 percent.

“For all the hullaballoo since Gingrich surged in support for the GOP presidential nomination, this poll, produced for ABC News by Langer Research Associates, finds that his favorable rating in his own party is unchanged from late last month, at 60 percent, and he’s actually grown more unpopular among independents and Democrats alike. The net result: No change in his favorable score, but a 6-point rise in the number of Americans who see him unfavorably.”

“Mitt Romney is sharpening his warning to Republicans about the consequences of nominating Newt Gingrich, declaring in an interview on Wednesday: ‘Zany is not what we need in a president.’

“‘Zany is great in a campaign. It’s great on talk radio. It’s great in print, it makes for fun reading,’ Mr. Romney told The New York Times. ‘But in terms of a president, we need a leader, and a leader needs to be someone who can bring Americans together.’…

“‘People are taking a closer look at Speaker Gingrich,’ Mr. Romney said. ‘And like other people who bumped up in the polls in this last year, as they take a closer look, some are happy with what they see and some would like to see something else and recognize that he may not be exactly what they wanted.'”

“David: More seriously, I’ve been asking smart people what they think the odds of Gingrich getting the nomination are. I myself put the odds at 25 percent. A week ago the average among the experts I spoke with was about 10 percent. More recently, it has surged to 30 percent among my cognoscenti friends…

“By the way, just because I said Gingrich has a 25 percent chance of getting the nomination doesn’t mean I think Romney has a 75 percent chance. I put him about 50. I’d give the other 25 percent to some unnamed senior party figure, like Jeb Bush. I figure that if Romney looks weak in South Carolina and Florida, then the party regulars mobilize and drag somebody else into the race. Even at that late date, that person could compete in some big primaries. If Bush were in the race now, he’d be the easy frontrunner.”