By Kay Henderson

DES MOINES, Iowa (Reuters) - Republican Mitt Romney attacked rival Mike Huckabee for criticizing President George W. Bush's foreign policy on Wednesday, while a new poll showed the race among Democrats in Iowa still neck-and-neck.

As candidates revved up their campaigns before taking a brief Christmas break, some released advertisements evoking the holiday spirit, including one from Republican Rudy Giuliani that featured Santa Claus.

All were light-hearted and none of them provoked the criticism that Huckabee did earlier in the week with a "Merry Christmas" advertisement that included a book shelf behind him that looked like a cross.

Huckabee, a former Baptist preacher seeking support from Christian evangelicals in Iowa, rejected criticism of the ad.

Iowa on January 3 starts the state-by-state process to pick the Democratic and Republican candidates who will face off in the presidential election on November 4, 2008. A win in Iowa can generate momentum for the battles to come rapidly afterward.

Romney, who has lost a big lead to Huckabee in Iowa, sought to raise doubts about his rival's foreign policy credentials, saying his criticism of Bush's foreign policy was more suitable for a Democrat than a Republican.

Last week, Huckabee said the Bush administration's "arrogant bunker mentality has been counterproductive at home and abroad" and promised that he as president would reach out to the rest of the world.

"I think Gov. Huckabee made a significant error in insulting the president as being subject to an arrogant bunker mentality," Romney said in Davenport, Iowa. "I disagree with that. I think the president is a man who has acted out of a desire to do what is right for America."