Chalk up another Republican presidential candidate who is not likely to gain Donald Trump's endorsement Mitt Romney. Romney on Tuesday said that he will not participate in the GOP debate scheduled to air on the ION network on December 27th that will be moderated by Trump. Interviewed by Neil Cavuto on Fox News, Romney said that he called Trump earlier in the day to inform him that he had to spend the month of December on the campaign trail and focusing on two other debates he had agreed to participate in during the month. "He understood my perspective and wished me well," Romney said. His decision was slammed later by Republican presidential frontrunner Newt Gingrich, who had no objection to the debate being compared with Trump's TV show, The Apprentice -- suggesting that the format might be "something that just sort of breaks out." Bringing Trump into the "environment" of a political debate, he added, "will actually be amazing." While Trump has suggested he might launch a third-party candidacy of his own after Celebrity Apprentice concludes this season, some political pundits have predicted he might endorse a candidate at the end of the debate, a possibility that Gingrich may have had in mind during his comments about Trump's role in the debate.