WEST DES MOINES, Iowa – With Iowa Republicans starting to make up their minds – and shuffling the deck of candidates – the 2012 presidential contest turned emotional Friday, just days before the state's caucuses kick off the voting for a GOP nominee.

Mitt Romney dropped his steel-eyed focus on potential general-election opponent Barack Obama to turn his fire on Texas Rep. Ron Paul, calling his chief rival in Iowa a fringe candidate.

Newt Gingrich, watching his support plunge under a withering assault of negative TV ads, choked up at one campaign stop while talking about his late mother, wiping away tears.

And Rick Santorum reveled in a last-minute surge of support after months of methodically working the back roads of Iowa, meeting voters one by one.

Their moods were buoyed – or dashed – as a new poll Friday showed Romney and Paul neck and neck at the top of the field, with Santorum, Rick Perry and Gingrich battling for third place. Michele Bachmann trailed far behind, and fewer than one in 10 likely caucus attendees was still undecided, according to the NBC News-Marist Poll.

The survey also underscored the late-breaking trends in the state as voters make up their minds, with Santorum gaining the most and Gingrich dropping fast. The latest numbers:

• Romney, the former Massachusetts governor, had the support of 23 percent, a gain of four points since Marist last polled Iowa earlier this month.

• Paul, the Texas congressman, had 21 percent, up two points.

• Santorum, a former senator from Pennsylvania, had 15 percent, up nine points.

• Perry, the governor of Texas, had 14 percent, up four points.

• Gingrich, the former speaker of the House of Representatives, had 13 percent, down 15 points.

• Bachmann, a congresswoman from Minnesota, had 6 percent, down one point.

• Former Utah Gov. Jon Huntsman, who's not campaigning in Iowa, had 2 percent.

• Undecideds numbered 7 percent, down two points.

Now relishing a shot at winning the state he wooed and lost in 2008, Romney took a swipe at Paul, the libertarian who promises to slash federal spending by $1 trillion in one year and vows a mind-our-own-business foreign policy criticized by many Republicans as isolationist.

"I don't think Ron Paul represents the mainstream," Romney said in an interview Friday with Fox News. "I'm working harder than anyone to make sure he's not the nominee."

Paul did not immediately respond – though his TV ads slam Romney as a flip-flopper.

In an outdoor rally in West Des Moines, Romney was joined by New Jersey Gov. Chris Christie, who recalled how Obama painted himself four years ago as the candidate of hope and change. "We are hopeless and changeless, and we need Mitt Romney to bring us back," Christie said.

Santorum basked in his rapid increase in support. He aired a new TV ad, while his campaign made an urgent appeal for cash.

"The Santorum surge is continuing," campaign manager Mike Biundo said in an email to supporters. "If we can keep the momentum going we are in great position to bring about an Iowa surprise."

At the same time, the man who's fast losing support, Gingrich, grew emotional during a stop in Des Moines. Gingrich's eyes filled with tears when he was asked during a town-hall meeting about his mother, Kit Gingrich, who died in 2003.

"You'll get me all teary-eyed," said Gingrich, wiping his eyes. "I identify my mother with being happy, loving life. … She had bipolar disease and depression … and that introduced me to the issue of long-term quality care."

He added, "I do policy much easier than I do personal."

Fickle throughout the summer and fall, Iowa Republicans now are firming up their choices as the precinct caucuses approach Tuesday evening. The NBC-Marist Poll found 53 percent saying they strongly support their choice, up from 40 percent at the beginning of December.

Santorum has the most solid support, with 59 percent of his backers saying they're firmly committed. Next is Paul, with 54 percent firmly committed; Perry with 52 percent; Romney with 51 percent; and Gingrich with 46 percent.

Digging deeper, the survey suggests that some candidates – Romney, Perry and Santorum in particular – have room to gain more support, while Paul may be near his ceiling.

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Reach Steven Thomma at sthomma@mcclatchydc.com