President Barack Obama and presumptive Republican nominee Mitt Romney are deadlocked in three key presidential battleground states, according to a new round of NBC-Marist polls.

In Iowa, the two rivals are tied at 44 percent among registered voters, including those who are undecided but leaning toward a candidate. Ten percent of voters in the Hawkeye State are completely undecided.

Read the full Iowa poll

In Colorado, Obama gets support from 46 percent of registered voters, while Romney gets 45 percent.

Read the full Colorado poll

And in Nevada, the president is at 48 percent and Romney is at 46 percent.

Read the full Nevada poll

These three states are all battlegrounds that Obama carried in 2008, but George W. Bush won in 2004.

“These are very, very competitive states,” says Lee Miringoff, director of the Marist College Institute for Public Opinion, which conducted these polls. “Everything is close.”

Results from NBC-Marist polling in three other battleground states released last week – Florida, Ohio and Virginia – showed Obama with narrow leads in each state.

Optimism, pessimism and enthusiasm
In Colorado, Iowa and Nevada, a more optimistic attitude about the U.S. economy is working in Obama’s favor. Majorities in each of the three states believe the worst is behind us, rather than yet to come.

In addition, majorities in these states say that the president mostly inherited the current economic conditions. 

But what seems to be hurting Obama – and helping Romney – is a sense that the nation is on the wrong track, with 54 percent in Iowa, 55 percent in Nevada and 56 percent in Colorado sharing that belief.

First Thoughts: Still fighting on GOP turf

Asked which candidate would do a better job on the economy, respondents in Colorado (45 percent to 42 percent) and Iowa (46 percent to 41 percent) picked Romney over Obama. But the two men were tied in Nevada (44 percent to 44 percent). 

What’s more, Romney leads Obama in Colorado and Iowa among those expressing a high level of enthusiasm, while the president leads among those voters in Nevada.

Obama’s approval rating, Nevada’s Senate race
The NBC-Marist poll also shows that Obama’s approval rating is above water in Iowa (46 percent approve, 45 percent disapprove), and it’s underwater in Colorado (45 percent to 49 percent) and Nevada (46 percent to 47 percent)

And in Nevada’s competitive Senate contest, the survey finds incumbent Republican Sen. Dean Heller in a tight race with Democrat Shelley Berkley, with Heller getting 46 percent among registered voters and Berkley getting 44 percent.

These NBC-Marist polls were conducted May 22-24 by landline and cell phone of 1,030 registered voters in Colorado, 1,106 registered voters in Iowa and 1,040 registered voters in Nevada. The margin of error in all three surveys is plus-minus 3.0 percentage points.

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Updated at 8:15 a.m. ET

Former Massachusetts Gov. Mitt Romney eked out a razor-thin victory in Tuesday night’s Iowa Republican caucuses, holding off former Pennsylvania Sen. Rick Santorum’s late-in-the-game-surge to win.

Win Mcnamee / Getty Images

Republican presidential candidate Mitt Romney on Jan 3.

After a night that saw the two candidates claim the lead, the GOP announced that Romney beat Santorum by just eight votes to become the apparent winner. Ron Paul finished third.

Romney and Santorum remained virtually tied as returns came back throughout the evening in this cycle's first nominating contest.  At the conclusion, each ended up at almost exactly a 25 percent share of the vote.

Chairman of the Iowa Republican Party, Matt Strawn, announced Romney got 30,015 votes and Santorum received 30,007 votes out of a record turnout of 122,255.

The result represented a dramatic closing act by Santorum to cement a furious, last-minute surge during which conservatives rallied around his campaign.

"Game on!" the jubilant ex-senator declared in remarks shortly after midnight.

The results were also humbling to an extent for the Romney campaign, which had appeared so confident in victory that it planned an overnight stay for the candidate in Iowa tonight instead of New Hampshire, where Romney's built a firewall. The former governor had also appeared to predict victory in a Monday night speech.

Andrew Burton / Getty Images

U.S. Sen. Rick Santorum addresses an Iowa crowd on January 3.

Texas Rep. Ron Paul finished third, at 21 percent. 

Three other candidates, former House Speaker Newt Gingrich, Texas Gov. Rick Perry and Minnesota Rep. Michele Bachmann had also sought to beat expectations and rejuvenate their candidacies in subsequent primary contests in New Hampshire and South Carolina.

Gingrich had the edge, at 13 percent, over Perry (10 percent) while Bachmann finished in sixth, at 5 percent.
Perry said he would take the next few days to re-assess his campaign.

"I've decided to return to Texas, assess the results of tonight's caucus, determine whether there is a path forward for myself in this race," he said in remarks shortly before midnight.

But the story of the night was Santorum, who managed to rally conservatives, who'd searched desperately throughout the campaign for an alternative to Romney, after other would-be contenders washed out throughout the fall.

Santorum noted "another candidate in this race," referring to Romney, whom pundits viewed as more electable. He paused when a member of his crowd said "RomneyCare," referring to the Massachusetts health reform law Romney had enacted but conservatives deplore for its similarities to President Obama's health care reforms.

"Let me tell you: What wins in America are bold ideas, sharp contrasts, and a plan that includes everyone," Santorum said.

"We are off to New Hampshire," Santorum declared, "With your help and God's grace we'll have another fun night a week from now."
Romney, by contrast, continued to act like the campaign's frontrunner in the evening's last remarks. He congratulated Santorum and Paul on a well-fought campaign, but trained most of his criticism on President Obama. 

Photo Blog: Caucus day photos from Iowa

In the end, Romney essentially matched his vote total from 2008, though he invested much less time and money in Iowa this cycle. But he failed to deliver the knock-out blow that his campaign had hoped for by playing in Iowa, and the results underscore the existing narrative in the campaign, that Romney is struggling to win over skeptical conservatives.

Sensing that Romney is vulnerable, the campaign now seems poised to move into a new phase in which the former Massachusetts governor will suffer more scrutiny.

Gingrich presaged this new phase in his remarks Tuesday evening, in which he vowed to continue his campaign beginning Wednesday in New Hampshire. He assailed Paul and Romney, too, while congratulating Santorum for running a positive campaign, and pointedly noted he wished he could say the same for other candidates, meaning Romney.

"We are not going to go out and run nasty ads," said Gingrich, who labeled Romney a "Massachusetts moderate" again. "But I do reserve the right to tell the truth. And if the truth seems negative, that may be more of a comment on his record than the nature of politics."

Santorum punched his ticket out of Iowa in part by emerging as the winner of a virtual game of musical chairs among candidates in Iowa who had themselves as the anti-Romney candidate. The former Pennsylvania senator had campaigned in Iowa the “traditional” way, having started to stump there well before any candidate, and becoming the first candidate to visit all of the state’s 99 counties.

The former Pennsylvania senator performed best among caucus-goers who describe themselves as very conservative, according to entrance poll data. He also won over evangelical Christians and caucus attendees who tabbed social issues as one of their priorities.

Romney had hoped to score a knock-out punch in Iowa after having scarcely competed in the race until later this fall. His campaign is hoping that a late push in Iowa, plus a victory next Tuesday in New Hampshire (where Romney leads in the polls), could all but clinch the nomination.

The Hawkeye State had ended up as Romney’s Achilles Heel in 2008. After having invested heavily in winning the contest, Romney limped out of Iowa after a disappointing second place finish.

Romney tied his 25 percent share of the caucus tally he earned in 2008 by attracting the support of caucus-goers who valued electability and the economy -- core elements of Romney's 2012 message. The most deeply conservative caucus participants shied away from Romney.

In a sign that the establishment was undaunted by Romney's finish, Sen. John McCain -- the 2008 GOP nominee and Romney's sparring partner from that cycle -- was set to back Romney on Wednesday in New Hampshire.

The results raise the stakes for the primary in New Hampshire, scheduled for Jan. 10, and two subsequent primaries in South Carolina and Florida in the second half of this month.

There are two debates scheduled for this coming Saturday and Sunday, which might provide the springboard for a new, naster stage of the campaign, with the scrutiny focused on Romney.

Paul, meanwhile, managed a third place finish by leaning on an unorthodox coalition of libertarian Republicans, young caucus-goers and independents.

"We will go on, we will raise the money," he told supporters this evening. He'll head next to New Hampshire.

His campaign, both in 2008 and 2012, has been notable for its intense enthusiasm from supporters and prolific fundraising. And in Iowa, where the strength of a candidate's organization typically correlates with a strong performance, Paul is hoping his well-organized supporters can help secure victory.

But his foes had also assailed his foreign policy views, which emphasize a limited role for the U.S. on the world stage. In a traditionally hawkish party, it’s led some political observers to suggest that Paul might have a difficult time building a broad coalition of support within the GOP.

Tuesday's results also raise fresh questions about the viability of Perry and Bachmann, who each spent heavily to win only fifth and sixth-place finishes, respectively. Bachmann made no indication of the future of her campaign during remarks late Tuesday evening.
For their parts, Bachmann and Perry have said before tonight they’ll head to South Carolina, which hosts its primary -- the third nominating contest -- on Jan. 21.

In a sign he's playing the long game, though, Romney has scheduled a trip to South Carolina overnight on Thursday and Friday morning. He’s also running ads in the Palmetto State, and announced Tuesday that he’s begun running ads in Florida, which hosts the next primary, as well.

Former Massachusetts Gov. Mitt Romney and Texas Rep. Ron Paul are running neck-and-neck in Iowa, former Pennsylvania Sen. Rick Santorum is surging and former House Speaker Newt Gingrich collapsing just four days before the state's Jan. 3 caucuses, according to a new NBC News-Marist poll.

Romney drew the support of 23 percent of likely caucus-goers in Iowa – identified based on interest, chance of voting and past participation – ahead of Paul, at 21 percent.

They are followed by Santorum at 15 percent, Texas Gov. Rick Perry at 14 percent, Gingrich at 13 percent and Minnesota Rep. Michele Bachmann at 6 percent.

The poll numbers, which are similar to those published in a recent CNN/Time survey, represent a reversal of fortune for Gingrich, as well as an improvement for Santorum and (to a lesser extent) Perry. The NBC-Marist poll conducted in late November had Gingrich in the lead among likely caucus-goers at 28 percent, Romney and Paul tied at 19 percent, Perry at 10 percent, Bachmann at 7 percent and Santorum at 6 percent.

• NBC News's guide to Iowa and New Hampshire

“More than half of [Gingrich’s] support has evaporated,” said Lee Miringoff, the director of the Marist College Institute for Public Opinion, which conducted the survey.

Negative advertising hits Gingrich 'on the chin'
Miringoff adds that the millions of dollars in negative TV ads targeting Gingrich – from a pro-Romney Super PAC and the Paul campaign – have played a major role in this erosion, with 35 percent of likely caucus-goers now saying he’d be unacceptable as the GOP’s nominee. That’s a 19-point increase from last month.

What’s more, only 6 percent in the survey identify Gingrich as the “true conservative” in the Republican contest.

“He took it on the chin,” Miringoff says of the negative advertising campaign, which has questioned Gingrich’s conservative credentials and tied him to Washington.

Splintered Tea Party support
Although just 7 percent of likely Iowa caucus-goers believe that Romney is the true conservative in the GOP field, he has two variables working in his favor, according to the poll. One, only 21 percent of likely caucus-goers say he’s unacceptable as the Republican nominee (compared with 35 percent for Gingrich and 41 percent for Paul).

And two, the conservative vote appears to be splintering between the various candidates, and is no longer coalescing around a single Romney challenger.

Last month, Gingrich had a large lead over Romney (and the other GOP rivals) among Tea Party supporters.

But in this new poll, Tea Party supporters – who make up about half of all likely caucus-goers – are divided.

Santorum gets 20 percent from them, Romney and Paul 17 percent, Gingrich 16 percent, Perry 15 percent and Bachmann 10 percent.

“This is the Romney dream scenario,” Miringoff says. “When you look at the Tea Party and conservatives, they are all splintered.”

Obama’s approval rating ticks up in Iowa
The poll also shows an improvement in President Barack Obama’s approval rating in Iowa.

Forty-five percent of registered voters in the state approve of him, while 43 percent disapprove.

Last month, those numbers were upside down, with 43 approving and 46 disapproving.

The Iowa NBC-Marist survey was conducted Dec. 27-28 of 2,905 registered voters (margin of error of plus-minus 1.8 percentage points) and of 433 likely GOP caucus-goers (plus-minus 4.7 percentage points).

Also, unlike the recent CNN-Time poll, the likely voter model in the NBC-Marist survey included independents and a few Democrats, and it measured some respondents by cell phone.

Follow Mark Murray (@mmurraypolitics) on Twitter.

More from First Read:

• Paul's surge might help Romney in Iowa
• Bachmann campaign loses 2nd key staffer in Ron Paul flap
• Huntsman says Paul is 'unelectable'
• Pro-Gingrich Super PAC: Romney is '2nd most dangerous man in America'

Jeff Haynes / Reuters

Massachusetts Governor Mitt Romney (L) speaks as former U.S. House Speaker Newt Gingrich (R-GA) looks on during the Republican Party presidential candidates debate at Drake University in Des Moines, Iowa.

Last updated at 11:32 p.m. ET.

The emerging political rivalry between Newt Gingrich and Mitt Romney simmered during Saturday night's GOP presidential debate, but at no point boiled over during the two-hour gathering. 

The former House speaker and the former Massachusetts governor sniped at each other throughout the debate, seeking to draw contrasts with each other at a debate at Drake University just 24 days before Iowans participate in the state's Jan. 3 caucuses.

The other four presidential hopefuls, meanwhile, took turns piling on Gingrich, the newly-minted frontrunner according to polls, and Romney, the candidate who's been consistently toward the top of the field throughout the campaign, but hasn't been able to seal the deal with conservatives.

The Gingrich-Romney spat was most stark during the first half hour of the debate, when Romney and Gingrich went at each other over their own political backgrounds. Romney stressed his private sector experience versus GIngrich's time in Congress.

RELATED: Gingrich in spotlight in pivotal debate

"Let's be candid: the only reason you didn't become a career politician is because you lost to Teddy Kennedy in 1994," Gingrich said in response, delivering a zinger in Romney's direction. "It's a bit much; you'd have been a 17-year career politician if you'd won."

Romney also lampooned some of Gingrich's more unconventional policy proposals.

"Speaker Gingrich and I have a lot of areas where we disagree," Romney said. "We can start with his idea to have a lunar colony that would mine minerals from the moon."

The two candidates sparred lightly throughout the rest of the debate, all while weathering criticism from the rest of the field.

Minnesota Rep. Michele Bachmann linked Gingrich and Romney together on the issue of a health insurance mandate, coining a new moniker to tie Romney and Gingrich together. She said the answer for GOP voters "is Michele Bachmann, not 'Newt Romney.'"

Romney faced criticism, too, from Perry — his main opponent in past debates this fall — over the health reform plan he installed as governor. Perry renewed criticism based on a line in an edition of a book written by Romney, prompting the former Massachusetts governor to offer a $10,000 bet with Perry. It was an eyebrow-raising moment, given the optics of a multimillionaire offering to make a hefty bet, considering the Romney campaign's intent focus on the economy and the middle class.

The Democratic National Committee (DNC), which has been dogged in its criticism of Romney during the primary, picked up on the moment, emailing reporters a list of items the average American family could buy with $10,000.

"Mitt Romney is going to rue the day he offered a $10,000 bet in this debate," said a senior Democratic Party strategist. "Talk about a window in to his out-of-touch soul. And he did it in the same debate where he again called the payroll tax cut for the middle class a temporary band-aid."

The debate had been expected to feature sparring between Gingrich and Romney, each of whom are jockeying for the top spot in the polls. Romney's campaign previewed tonight's showdown by unleashing a wave of criticism of Gingrich the second half of this week.

But the other candidates also sought to use the debate as an opportunity to make a move in the polls, with precious days separating tonight's debate and the beginning of the voting process.

That meant more criticism of Gingrich, who's leapfrogged the pack and to the lead in a variety of state and national polls released this week. 

Texas Gov. Rick Perry, for instance, made a thinly-veiled reference to Gingrich's three marriages and past infidelity. Perry said that the candidates' personal lives should be an element for consideration by primary voters. 

"if you cheat on your wife, you'll cheat on your business partner," said Perry, who's been making a play of late for social conservative voters in Iowa. "I think that issue of fidelity is important." 

And the moderators added new scrutiny of Gingrich, too. The former Speaker found himself under newfound scrutiny at this debate associated with his ascendancy in the polls. He was pressed, for instance, by moderators about his statement this week calling Palestinians an "invented" people.

Gingrich stood by that characterization, and even went further in his characterization of some Palestinian groups: "These people are terrorists."

But the emerging Romney-Gingrich feud was the most closely-watched plot line of the debate, the 12th among Republicans during this primary cycle. While their exchanges weren't always the most fiery, another debate in Iowa scheduled for Thursday could further the divide between the two of them.

Romney perhaps best summed up his criticism of Gingrich in a later exchange between the two over Israel: "I'm not a bomb-thrower, rhetorically or literally."

The debate setting has been where Gingrich, whose debt-saddled campaign was left for dead this summer after suffering a mass resignation by senior staff, has thrived. His resurgence has been driven by strong debate showings. 

These gatherings have been of unusual influence in the primary, in part due to the fluidity in the polls. A majority of Republicans in key primary states said in a poll this week that they still may change their mind. 

The debate was broadcast on ABC and co-sponsored by the Des Moines Register.