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By MICHAEL FALCONE ( @michaelpfalcone ) and AMY WALTER ( @amyewalter )

COLUMBIA, S.C. - With just three full days of campaigning left before this weekend's crucial South Carolina primary, it looks like Newt Gingrich is getting under Mitt Romney's skin.

Here's a clue: The Romney campaign has scheduled a morning conference call with two of the former Massachusetts governor's most ardent backers to discuss "Speaker Gingrich's Record As An Unreliable Leader."

Former U.S. Sen. Jim Talent and former New York Congresswoman Susan Molinari will do the honors as the Newt bashing kicks into higher gear with time running out for Romney to cement his lead in the polls here and for Gingrich or another challenger to catch up with him.

For his part, Newt seized on the opportunity to tweak Romney yesterday after learning in an interview with ABC's Jonathan Karl that Romney pays roughly a 15 percent tax rate. In fact, the former House Speaker called on Romney to endorse his 15 percent flat tax plan.

"I'm thrilled at the idea that Mitt, I assume this afternoon will endorse my flat tax proposal and have every American pay it the way he paid," Gingrich said, adding: "I think we ought to rename our flat tax, we have a 15 percent flat tax, so this would be the 'Mitt Romney flat tax,' all Americans would pay the rate Mitt Romney paid, I think it's terrific," Gingrich said. http://abcn.ws/yGHByH

Gingrich and his campaign have been trying to leverage a strong debate performance on Monday night into votes, and they're getting some help from a pro-Gingrich super PAC, Winning Our Future, that released a new campaign ad overnight highlighting Gingrich's prowess on the debate stage.

Meanwhile, before flying to New York yesterday for a fundraiser, Romney faced a series of questions over how much he pays in taxes and when he plans to release his returns. He also looked out of touch when he told reporters in Florence, S.C. that "I get speakers fees from time to time, but not very much." (Turns out that Romney actually pocketed nearly $375,000 in speaking fees in 2010.)

Not helping matters were the words of one of Romney's most prominent backers, New Jersey Gov. Chris Christie, who urged the candidate this morning to make his tax returns public.

"I've released all of my tax returns," Christie said on MSNBC's "Morning Joe" today, "and I released them every year after I filed them, right after I filed them to the public of New Jersey so they can see everything. And I think that's the right way to go and that's what I would tell Gov. Romney to do."

It's not exactly the message the Romney campaign wants in voters' minds heading into primary day, but the Gingrich clan couldn't be happier.

NEWT'S PALIN BOUNCE? Just one week after her husband Todd Palin "went rogue" and endorsed Republican presidential candidate Newt Gingrich, former vice presidential candidate Sarah Palin said tonight she would vote for Gingrich "if I were a South Carolinian" - the closest she has come to an endorsement in this race, reports ABC's Elicia Dover. Fox News' Sean Hannity asked Palin if she was any closer to an endorsement of a presidential candidate. "If I had to vote in South Carolina, in order to keep this thing going I'd vote for Newt and I would want this to continue," Palin said. "More debates, more vetting of candidates because we know the mistake made in our country four years ago was having a candidate that was not vetted, to the degree that he should have been so that we knew what his associations and his pals represented and what went into his thinking, the shaping of who our president today is." http://abcn.ws/w40OSL

ABC's Jon Karl reported for "Good Morning America" on the state of the GOP race in South Carolina. WATCH: http://abcn.ws/yS5uFL

ROMNEY SENT MILLION TO MORMON CHURCH. "Underscoring the prominent, if little discussed role that Mitt Romney played as a Mormon leader, the private equity giant once run by the GOP presidential frontrunner carved his church a slice of several of its most lucrative business deals, securities records show, providing it with millions of dollars worth of stock in some of Bain Capital's most well-known holdings," ABC's Matthew Mosk and Brian Ross report. "Romney has always been a major donor to the Church of Jesus Christ of Latter-day Saints, which requires that members 'tithe,' or give 10 percent of their income to the church. His family charity, called the Tyler Foundation, has given more than $4 million to the church in the past five years, including $1.8 million in 2008 and $600,000 in 2009. But because Romney, whose fortune has been estimated at $250 million, has never released his personal tax returns, the full extent of his giving has never been public. Newly uncovered stock contributions made during Romney's Bain days suggest there is another dimension to Romney's support for the church - one that could involve millions more than has been previously disclosed." http://abcn.ws/y2yRU5

THE BUZZ

NEW ROMNEY SUPER PAC AD ATTACKS SANTORUM (AGAIN). ABC's Emily Friedman reports: A new ad from the pro-Romney SuperPAC "Restore our Future" released this morning focuses again entirely on Sen. Rick Santorum, dubbing the former Pennsylvania senator "the ultimate Washington insider." Absent from this ad, however, is any reference to Santorum's support of felons voting rights', which became an issue during Monday night's debate when Santorum challenged Romney on the issue following a Restore our Future ad titled "Facts" that said that Santorum "voted to let convicted felons vote." "Governor Romney's super PAC has put an ad out there suggesting that I voted to allow felons to be able to vote from prison, because they said I'm allowing felons to vote, and they put a prisoner - a person in a prison jumpsuit," said Santorum during the Fox News/WSJ debate Monday night. " I would ask Governor Romney, do you believe people who have - who were felons, who served their time, who have extended - exhausted their parole and probation, should they be given the right to vote?"

SANTORUM PUSH BACK: "He's playing dirty, dishonest politics and he's standing behind this super PAC when, in fact, he's not standing behind it anymore. He' s now saying that what they are doing, the lie they are putting out there, is a lie that he is going to stand behind," Santorum said yesterday. http://abcn.ws/zAJuVi

SANTORUM UNLEASHES ANTI-ROMNEY ATTACK MAILERS. Rick Santorum is keeping his promise to sharpen the contrast with Mitt Romney in a new mailer arriving in the homes of South Carolina voters with just four days to go before Saturday's primary. The mailer greets residents with an unmistakable message: "Mitt Romney Is Hoping You Never Read This." It pits Santorum ("a trusted conservative) against Romney ("the moderate"), according to a copy of the piece of campaign literature obtained by ABC News. On the campaign trail this week, Santorum has been lashing out at Romney for refusing to take steps to rein in his super PAC allies who have been running negative ads against the former Pennsylvania senator. Santorum's mail-box offensive against Romney is just one example of the ground war among the campaigns that is playing out across the state and taking the form of mailers, fliers, and automated telephone calls. "You can't turn on the TV without seeing a vicious negative attack ad by Mitt Romney," the Santorum mailer reads. "Not only are the ads insulting and offensive, they're downright false. And clearly Romney was hoping you wouldn't have time to find out. Now you do." See the mailer: http://abcn.ws/zN30Ih

PERRY PRAYS WITH SOUTH CAROLINA VOTERS. Days before the South Carolina primary, Rick Perry led The Response, an offshoot of the August event he helped organize in Texas which drew a crowd of 30,000 plus people, in prayer and scripture reading, ABC's Arlette Saenz reports. The Texas governor's speech modeled many of the same themes as his August appearance, calling God a "personal God" who is unaffiliated with any political party.  Earlier in the day, Perry criticized Rick Santorum's social conservative record, saying his vote for Sonia Sotomayor's appointment to an appellate court reveals questions about his true conservative background.  The Texas governor also made it a point to stress that Santorum is a "good Catholic" -  two times.  According to a recent Gallup poll, 74 percent of the people of South Carolina identify themselves as protestant or non-Catholic, while only 10 percent are Catholic.  Perry himself was raised a Methodist but now attends a non-denominational mega-church in Austin. http://abcn.ws/AwXtmn

ABOUT THOSE DEBATE NIGHT BOOS…. ABC's Jason Volack reports that Ron Paul pushed back against critics of his "Golden Rule" in foreign policy and questioned those who booed him at Monday's GOP presidential debate. Speaking in Spartanburg, S. C. Tuesday afternoon, Paul referenced America's threats of an oil embargo on Iran. "This is why I bring up the "the golden rule" if we don't want people to ban oil imports to our country, why should we do that to another country," said Paul adding "I don't know why that is such a negative term for people to boo that. " Paul also said that America needs to do away with the idea that it will only talk to nations it deems as perfect adding only until America is itself perfect can it make such judgments.  The conservative Republican electorate in South Carolina booed Paul's answers on foreign policy and Texas Gov. Rick Perry even suggested that a gong should have been used to cut Paul off. Today, Paul takes a break from the campaign trail and returns to Washington to vote against the increase in the nation's debt ceiling. The fiscal conservative called Wednesday's vote a "gimmick" and said even if Congress votes it down it automatically goes into effect. "It's such a mess," said Paul. http://abcn.ws/AuyPaW

NOTED: Unlike like his GOP rivals, Paul doesn't feel the need to campaign nonstop. Paul took a break from the campaign trail right before the Iowa caucus on Jan 3 and after the Iowa caucuses he again took several days off to go home to Lake Jackson, Tex., to rest before campaigning in New Hampshire.

BIG PICTURE: HOW VULNERABLE IS OBAMA? Three new recent national polls should give Democrats some serious pause, ABC News Political Director Amy Walter notes. They show a very vulnerable president who is serious danger of losing re-election. ABC/Washington Post polling shows Obama's approval rating at 48 percent.  Pollster Gary Langer writes: "In polling since 1940, just four previous presidents have started their re-election year with less than 50 percent approval. Only one of them won, Richard Nixon in 1972." Gallup's Lydia Saad writes: " Obama's job approval rating has averaged 44 percent in Gallup Daily tracking since the start of January. That is below the approval rating of seven out of eight previous incumbents at a comparable point in their presidencies." CNN/ORC poll asked voters who they saw as best able to "get the economy moving." Just 40 percent chose Obama, while 53 percent picked Romney. ABC/Washington Post and CNN/ORC polling show Obama in a dead heat with Romney. http://abcn.ws/ylWqPQ

IN THE NOTE'S INBOX: Democratic Congressional Campaign Committee Chairman Steve Israel will hold a pen and pad briefing today "to announce the first wave of Red-to-Blue candidates and to discuss the 2012 landscape." Where? DNC Building, 430 S. Capitol Street, SE, Washington, DC. When? 11:30 a.m.

WHO'S TWEETING?

@JesseFFerguson : Big congrats to  @Lis_Smith - new rapid response director for  @BarackObama.

@RobSaliterman : Great profile of  @zacmoffatt: Doing Digital for Romney - The Atlantic bit.ly/zK0yR1

@GlennThrush : Why is Obama's super PAC struggling? Obama hates it. Will the king sacrifice his clean-hands …  m.tmi.me/kMdKw

@MaeveReston : Missing from Mitt Romney's arsenal: The common touch lat.ms/Aukk2C

DISPATCHES FROM THE TRAIL. Check out our new political website OTUSNews.com ( www.Otusnews.com) The Note ( http://abcnews.go.com/blogs/politics/the-note/) and ABC News/Politics ( http://abcnews.go.com/politics) and follow our reporters in the field on Twitter:

Newt Gingrich : ABC's Elicia Dover ( @EliciaDover)

Jon Huntsman : ABC's Susan Archer ( @TheOnlyArcher)

Ron Paul : ABC's Jason Volack ( @Jason_Volack)

Rick Perry : ABC's Arlette Saenz ( @ArletteSaenz)

Mitt Romney : ABC's Emily Friedman ( @EmilyABC)

Rick Santorum : ABC's Shushannah Walshe ( @shushwalshe) and ABC's Russell Goldman ( @GoldmanRussell)

Check out The Note's Futures Calendar:  http://abcn.ws/ZI9gV

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