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

MUSCATINE, Iowa - The candidate who may have the best shot at walking away with a win in the Iowa caucuses six days from today has become persona non grata among his Republican counterparts.

With his libertarian bent and his views on foreign policy that leave some of his fellow Republicans scratching their heads, Ron Paul is a threat of a different sort. And as pre-caucus polls continue to show him at the top of the pack in Iowa his opponents are swatting at him with fresh intensity.

Leading the charge yesterday was Newt Gingrich, who told CNN's Wolf Blitzer that he could not support the long-time Texas Congressman if he won the Republican nomination, characterizing his views as "totally outside the mainstream of virtually every decent American."

"I think the choice of Ron Paul or Barack Obama would be a very bad choice for America," Gingrich lamented.

Another rival, former Pennsylvania Sen. Rick Santorum, warned voters to carefully study Paul's record, which Santorum said puts him somewhere to the "left of Barack Obama on national security."

Santorum also pointed the crowd to Paul's time in Washington, noting that "he's been in Congress for 20 years and hasn't passed a bill." And he didn't stop there. Yesterday, Santorum, who is vying for one of what is likely to be three or four tickets out of Iowa, even took a shot at Paul's age, reminding his crowd in Mason City that the Texan is 78 years old.

Rick Perry, meanwhile, has been invoking Paul's controversial stance on Iran at campaign events and last week he accused Paul of being a pork-barrel politician.

"The Republicans stood up and said, "you know what, we're going to do away with earmarks, but there were four Republicans that didn't follow that, and Dr. Paul was one of them," Perry told voters in northern Iowa. "He had earmarks I think over the last two years approaching half a billion worth of these special interest earmarks."

For weeks, Minnesota Congresswoman Michele Bachmann, has been referring to Paul as "very dangerous" and while addressing Iowa voters during a stop on her whirlwind bus tour in Council Bluffs yesterday she asserted: "Ron Paul doesn't believe the government should protect the institution of marriage."

As ABC's Jason Volack notes, Paul is facing many questions concerning a decade's worth of incendiary newsletters published by the Texas Congressman and were written under his name. And he will likely continue getting asked about them as he gets back on the campaign trail in Iowa today. http://abcn.ws/s1kmDB

Nevertheless, Paul has a committed base that isn't going anywhere and will turn out rain, shine or snow. And, if the field is split in as many ways as it is now, Paul's low ceiling of 24-25 percent could be enough to win in Iowa.

IN THE NOTE'S INBOX: PAUL'S NEW AD: From the Paul campaign "The Ron Paul 2012 Presidential campaign released today a new television ad titled 'Machine' airing on television in the key early voting states of Iowa and New Hampshire.  The ad begins airing today. The 30-second ad condemns the dysfunctional Washington-insider atmosphere created and furthered by slick politicians, and presents Ron Paul as a leader who has stood apart and above such an environment." http://bit.ly/sqFJ0T

GINGRICH FALLS WHILE ROMNEY'S FLAT. A new Gallup polling shows Mitt Romney and Newt Gingrich now tied - Gingrich has shed 12 points since early December. Not a good narrative heading into the caucused for the former House Speaker. Still, it's worth noting that even as Newt has fallen, Romney hasn't picked up any support.  At some point he has to show that he can do more than keep steady - he's got to be able to show that he can grow.

ABC's Jonathan Karl notes that Gingrich is having a "man up" moment, telling his GOP rival Mitt Romney to take responsibility for the negative ads being run by super PACs supporting him. WATCH: http://abcn.ws/tcQvjA

THE NOTE ON THE ROAD. The Note boarded the Mitt Romney press express at 6:45 a.m. Iowa time to head to Elly's Tea and Coffee in Muscatine, Iowa where the former Massachusetts governor is holding his first event of the day. With the sun barely rising above the horizon on a chilly morning here, a line to see the candidate stretched out the door. The crowd this morning follows another over-flow event in Davenport last night. "Thanks for getting up this morning!" Romney said, cheerfully greeting voters. Romney's bus tour will take him to Clinton and North Liberty, Iowa later today.

ROMNEY OFFERS A CLOSING ARGUMENT TO IOWANS. ABC's Emily Friedman reports from Davenport, Iowa: In his final major speech to Iowa voters before next week's caucuses, Mitt Romney pivoted from his nearly around-the-clock focus on President Obama to target Vice President Joe Biden, encouraging supporters to pity the president's second-in-command. "You have to feel sorry for Joe Biden," Romney said, speaking in a ballroom at the Blackhawk Hotel in downtown Davenport, where Obama stayed a few months ago. "Four years ago, he warned us about Barack Obama. It turns out he was right. Now, every day, he has to keep quiet about that. And you know how hard that is for Joe." While Romney had joked last week on the campaign trail in New Hampshire that Biden's editorial in the Des Moines Register was just another "gaffe" by the politician who has come to be known for his off-the-cuff remarks, tonight's speech included a large chunk dedicated to the vice president. In the piece, Biden wrote that Romney "appears satisfied to settle for an economy in which fewer people succeed." http://abcn.ws/tWdFug

THE NOTE'S QUOTE: Mitt Romney in Davenport, Iowa Tuesday night: "This is an election not only to replace a President. It is an election to save the soul of America. It is a choice between two destinies."

Likely Iowa caucus-goer Jennie Barnds, a stay-at-home mom, who The Note spoke to after Romney's speech to an standing-room-only hotel ballroom in Davenport. Barnds walked into the event undecided; she walked out a Romney supporter. "I think its Mitt Romney," Barnds said, pausing for a moment. "I know its Mitt Romney. Like Mr. Romney said, this is an election about saving America's soul. … His personal background in business is what's extremely appealing. You need someone with a proven track record in the business sector."

DEMOCRATIC COUNTER-PROGRAMMING. "Rather than offering a plan to restore economic security for the middle class, Romney made it clear he would settle for an economy where fewer Americans succeed regardless of how hard they work," Iowa Democratic Chairwoman Sue Dvorsky said in a statement today. "After a year of pretending he wasn't competing here, Romney continues to try to downplay expectations for his performance in the Hawkeye State next week.  But the reality is that in the month of December alone, Mitt Romney's campaign and the Super PAC supporting his candidacy spent $4 million in Iowa - clearly, Romney is now all in to win in Iowa."

@ ABC :  Top Campaign Moments of 2011   http://abcn.ws/sCidgL

GOOD MORNING IOWA. Don't forget to check The Note blog every morning for the latest edition of "Good Morning Iowa" - a one-stop-shop tip-sheet covering everything you need to know from the Hawkeye State, reported by ABC's Shushannah Walshe.

DISPATCHES FROM THE TRAIL. Also, keep an eye on our new political website OTUSNews.com ( www.Otusnews.com) The Note ( http://abcnews.go.com/blogs/politics/the-note/) and on ABC News/Politics ( http://abcnews.go.com/politics) for rapid-fire updates from the campaign trail between now and the Iowa Caucuses. Follow our reporters in the field on Twitter:

Michele Bachmann : ABC's Russell Goldman ( @GoldmanRussell )

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

Jon Huntsman and New Hampshire: 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 and Iowa: ABC's Shushannah Walshe ( @shushwalshe )

 

PRIMARY COLORS.

-At one of Michele Bachmann's campaign stops in Guthrie Center, Iowa yesterday, Rep. Steve King's younger brother, a UPS worker, was in attendance. The younger King said he, like his brother, would not say whether or not he'd made a decision on who he would vote for.-ABC's Russell Goldman

-Before arriving in Iowa for his bus tour on Tuesday, Mitt Romney campaigned in New Hampshire where he compared Newt Gingrich's struggles getting on the Virginia primary ballot to the famous "I Love Lucy" chocolate factory episode. -ABC's Susan Archer http://abcn.ws/w0snpi

-Oops: An Iowa state lawmaker had  his own "oops" moment yesterday when he introduced Rick Perry as the "governor of California." Perry seemed to really enjoy his meet and greet at the Glenn Miller Museum in Clarinda, Iowa.  He told the crowd his father heard the Glenn Miller Orchestra play while he served in the military. -ABC's Arlette Saenz

- Newt Gingrich was endorsed by the architect of the Reagan Economic Plan, economist Arthur Laffer. He will campaign in Iowa for Gingrich Thursday. (Laffer previously endorsed Rick Perry for Governor of Texas.)  -ABC's Elicia Dover

THE BUZZ

GINGRICH CAMPAIGN - STILL IN DEBT. "Republican presidential candidate Newt Gingrich's campaign made a new ad buy today, the third of an expensive advertising in Iowa, keeping the campaign in debt, according to a spokesman," ABC's Elicia Dover reports. "A campaign spokesperson told ABC News today they would still have debt in the next FEC filing report because 'we're trying to win in Iowa.' The campaign would not release the purchase amount of the new ad, saying only that the buy was 'major.' The ad titled 'Winning the Argument,' will begin airing tomorrow and shows clips from Gingrich in past debates. The Gingrich campaign made two $250,000 ad buys in December, running two ads repetitively over the last month. The campaign is buying large amounts of ads instead of paying back debt, some of which include charter planes and debts owed from big spending early in the campaign season. ABC News reported last month that the Gingrich campaign did pay back the $42,000 owed to Gingrich himself for his list of contacts." http://abcn.ws/tBjfYe

ROMNEY 'RE-TOOLED.' The New York Times' Ashley Parker and Michael Barbaro take a look at the Mitt 2.0 on the campaign trail: "When Mitt Romney introduces himself to voters, he has a peculiar habit of guessing their age or nationality, often incorrectly. (A regular query: 'Are you French Canadian?') When making small talk with locals, he peppers the conversation with curious details. ('We stayed in the Courtyard hotel last night,' he told a woman at a diner. 'It's a LEED-certified hotel.') And when he encounters a question he particularly dislikes, he smiles politely and behaves as if it never happened. ('Will you put Ron Paul in your cabinet?' a man asked. The candidate turned away, inquiry left unanswered.) Mr. Romney's bid for president this year is a carefully crafted do-over, a chance to revise and retool a campaign that quickly fizzled out four years ago. He has lost the tie, overhauled his stump speech and hired far fewer campaign consultants. … A close-up study of Mr. Romney's casual interactions with voters captures a candidate who can be efficient, funny and self-deprecating, yet often strains to connect in a personal way." http://nyti.ms/tGFkI8

RICK PERRY TALKS UP 'TRANSFORMATION' ON ABORTION. ABC's Arlette Saenz files this dispatch from Osceola, Iowa: Rick Perry admitted to Iowa voters this evening that his views on abortion have undergone a "transformation," shifting from a stance that allowed for abortion in cases of rape, incest and risk to a mother's life, to one that opposes abortion in all forms. "You're seeing a transformation," Perry said in response to a voter's question about his changed stance at a town hall meeting here. "That transformation was after watching the DVD 'Gift of Life,' and I really started giving some … thought about the issue of rape and incest, and some powerful stories in that DVD." http://abcn.ws/udpivo

NOTED: "Lawyers for Gov. Rick Perry filed papers in federal court in Richmond Tuesday arguing that Virginia's requirement for petition circulators to be either eligible or registered voters in the state "imposes a severe burden" on Perry's freedom of speech," ABC's Ariane de Vogue notes. "Richard L. Hasen an election law expert at the University of California Irvine says that Perry's challenge faces 'long odds both politically and legally' in part because he filed suit after the filing deadline. On his election law blog Hasen writes, 'this is an emergency of Perry's (and Gingrich's) own making. Surely they knew of the requirement earlier.'" http://abcn.ws/tQNuwN

OCCUPY COMES TO THE CAUCUSES. "An offshoot of the Occupy Wall Street movement met Tuesday evening to organize and plan protests in Iowa's capitol during the week leading up to the state's caucuses next Tuesday," ABC's Shushannah Walshe reports. "About 200 people involved in the Occupy the Caucuses movement met in East Des Moines and split up into groups by the GOP candidates they want to "occupy" this week. Protestors have said they will also camp out outside President Obama's headquarters. At the beginning of the session, protesters aired grievances that they wanted to raise at the candidates' headquarters this week, and then attendees split into groups by candidate. The issues included ending the war in Afghanistan, campaign finance reform and higher education and health care costs, amongst other hot topics." http://abcn.ws/uAszDV

WHAT SEN. BEN NELSON'S RETIREMENT MEANS. "Democratic Sen. Ben Nelson survived nearly two decades representing heavily Republican Nebraska by carving a path down the political center. But faced with navigating that road in an increasingly polarizing climate, Nelson is stepping away - and swinging the door wide open for the GOP," according to the Associated Press. "Nelson, the lone Democrat in Nebraska's five-member congressional delegation, announced Tuesday that he wouldn't seek a third term. He was facing a tough campaign against several Republicans who've spent the past several months attacking his support for President Barack Obama's health care overhaul and federal stimulus legislation. … Other Democrats lamented Nelson's decision to retire, fearing it sets up the GOP for an easy victory next year. Republicans need to net just four seats to reclaim control of the Senate, and Nebraska looks to be an easy pickup. There are no Democrats in line to take Nelson's place in the increasingly conservative state. He joins several other Democrats to retire from the Senate, including Virginia's Jim Webb and North Dakota's Kent Conrad." http://wapo.st/uLwCOd

NOTED: ABC'S SENATE RETIREMENT CRYSTAL BALL. Our Capitol Hill guru Jonathan Karl notes: In January, after Kent Conrad and Joe Lieberman announced their retirements, ABC News put together a list of the seven Senators Most Likely to Retire.  With today's announcement that Ben Nelson won't run for reelection, all seven Senators on our list have now retired.  Seven for seven. FLASHBACK: http://abcn.ws/hQkjah

VIDEO OF THE DAY: 2011'S Top Campaign Moments in Under Two Minutes: Who jumped in, dropped out, and dropped the ball on the campaign trail? WATCH: http://abcn.ws/rNJFWo

 

WHO'S TWEETING?

@ gabrielsherman : Romney on F&F responding to Newt's ballot comments: "We all make mistakes, I don't compare those mistakes to Pearl Harbor."

@RealClearScott: Must Follow: Yahoo News' new elections Executive Producer @stevechaggaris

@ FixAaron : Pro-Gingrich Super PAC: Romney is '2nd most dangerous man in America'  on.msnbc.com/rHBAOX

@ BenPhilpottKUT : Bigger crowds-more press at  #RickPerry event this morning in Urbandale IA.  pic.twitter.com/yrTms3RX

@PeterHambyCNN : My story on how Rick Perry, once fatigued by back surgery, is back to running at full strength >  bit.ly/sP1nvK

 

POLITICAL RADAR.

- Mitt Romney is in Iowa where he'll make three stops on his bus tour. In Clinton, Romney will meet with voters to discuss jobs and the economy.

- Ron Paul will hold a town hall meeting in Newton, Iowa at the Iowa Speedway Media Center. Wednesday evening, Paul will host a Salute to Veterans rally at the Iowa State Fairgrounds.

- Newt Gingrich makes four stops on his Iowa Bus Tour kicking off in Mason City. Gingrich ends his day with an event at the Pizza Ranch in Le Mars.

- Rick Perry travels from Urbandale to Oskaloosa, Iowa hosting four events along the way. Steve Forbes will campaign for Perry in New Hampshire delivering a speech in Milford and attending a GOP Forum in Derry.

- Michele Bachmann continues her Iowa Bus Tour with 11 stops. Bachmann will start her day in Greenfield and end in Boone.

- Jon Huntsman is on the trail in New Hampshire hosting an evening town hall in Pelham.

-ABC's Josh Haskell

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

 

* Get  The Note delivered  to your inbox every day.

* For breaking political news and analysis check out The Note blog:  http://blogs.abcnews.com/thenote/ and ABCNews.com/Politics:  http://abcnews.com/politics