Updated at 12:30 p.m. ET
A new poll of likely Republican caucus-goers in Iowa shows Mitt Romney and Ron Paul running neck and neck for the GOP presidential nomination, but luckily for Romney, those voters also call Paul the most "unacceptable" candidate running.
As many as 41 percent of likely caucus-goers said they would find Paul "not acceptable as the Republican nominee for president," according to the new NBC News/ Marist poll, conducted December 27-28. Another 35 percent called Paul an acceptable candidate, while 21 percent said they would find him acceptable, but they would have reservations about his candidacy.
By contrast, 21 percent said Romney would be an "unacceptable" candidate. Fifty percent said he would be "acceptable," while 27 percent answered "acceptable but with reservations."
The other candidates -- Newt Gingrich, Rick Perry, Michele Bachmann and Rick Santorum -- fell in between Romney and Paul on that question.
Despite the difference between the two candidates on whether they would make "acceptable" candidates, Romney and Paul are the two frontrunners in the polls. Twenty-three percent of likely caucus-goers said they support Romney, while 21 percent support Paul. Santorum came in third with 15 percent support, followed by Perry at 14 percent and Gingrich at 13 percent.
The poll mirrors the results of thereleased this week, which also showed Romney and Paul statistically tied in Iowa, with Santorum surging.
Polls suggest that Paul has a natural ceiling of support among GOP voters, largely because of his non-interventionist foreign policy views. A recent Washington Post/ABC News poll found that nearly half of Republican voters feel Paul's foreign policy views are a major reason not to vote for him. Still, as Hotsheet has, Paul has the best get-out-the-vote organization of any candidate in the state, and a victory there would go a long way toward pushing his libertarian views into the mainstream.
Other responses in the NBC poll also appear to fall in Romney's favor. For instance, when asked to name what's most important to them in deciding who to support, 30 percent of likely caucus-goers said a candidate who shares their values -- but nearly as many, 28 percent, said a candidate who can beat President Obama in 2012.
Support from the conservative Tea Party wing of the party in the latest poll appears to be split among Romney's rivals, with Santorum taking the biggest share at 20 percent. Gingrich last month had strongest Tea Party support.