Romney, Paul close in Iowa race: poll

Former Massachusetts Governor Mitt Romney (L) listens to Rep. Ron Paul (R-TX) speak at the Republican presidential debate at Dartmouth College in Hanover, New Hampshire October 11, 2011.

(Reuters) - Mitt Romney holds a narrow lead in Iowa in the race for the Republican presidential nomination, according to a poll released on Friday that also showed significant concern on whether his closest rival, Ron Paul, would be an acceptable nominee.

According to the NBC/Marist poll, 23 percent of likely participants in Tuesday's Iowa caucuses said they would support Romney, a former Massachusetts governor, and 21 percent backed Texas Congressman Paul.

But 41 percent of likely voters in the survey said they believed Paul, with his libertarian and isolationist messages, would be unacceptable as the Republican nominee.

Former Pennsylvania Senator Rick Santorum came in third with 15 percent, continuing his late surge in Iowa, a state where he has focused much of his efforts in hopes that his social conservative message would resonate with evangelical Christian voters.

Santorum was followed by Texas Governor Rick Perry with 14 percent, and former House of Representatives Speaker Newt Gingrich, who has seen his support crumble, had 13 percent.

Gingrich has been hit with negative advertisements and was criticized for poor organization after he failed to qualify for the primary ballot in Virginia. Perry, meanwhile, is looking for a boost after a wave of his Texas supporters arrived in Iowa to volunteer with his campaign.

The survey of 425 likely Republican caucus-goers, including some independents and Democrats who might caucus as Republicans, was conducted December 27-28. The results, which had a margin of error of plus or minus 4.8 percentage points, are similar to a CNN/Time poll also in Iowa this week.

(Reporting By Emily Stephenson; Editing by Vicki Allen)