DES MOINES, Iowa - December 30, 2011 - 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’s candidacy is 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% of likely caucus-goers in Iowa - identified based on interest, chance of voting and past participation - ahead of Paul, at 21%.

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

The poll numbers 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%, Romney and Paul tied at 19%, Perry at 10%, Bachmann at 7%, and Santorum at 6%.