Busy Day Both Tests and Rewards Gingrich A frenetic swirl of developments in the Republican presidential campaign over the last 24 hours is testing whether Newt Gingrich can manage tricky political crosscurrents as he seeks to emerge as the undisputed alternative to Mitt Romney. The decision by Gov. Rick Perry of Texas to abandon his campaign and heartily endorse Mr. Gingrich just two days ahead of voting in the South Carolina primary comes as new polling suggests that Mr. Gingrich is gaining ground in the state. Mr. Romney's lead over Mr. Gingrich in South Carolina has been cut in half in the last two weeks, recent polls show. And the perception of inevitability behind Mr. Romney's march toward victory was further shaken on Thursday morning by official results in Iowa, which erased his victory in the Republican caucuses. The timing couldn't be worse for Mr. Romney - or better for Mr. Gingrich. The two men will debate again tonight, joined by Rick Santorum and Representative Ron Paul, for yet another round in what has easily become Mr. Gingrich's most effective forum. In the face of millions of dollars in attacks from rivals and "super PACs," Mr. Gingrich has repeatedly used the many nationally televised debates to rekindle the belief in voters that he is be the best person to confront President Obama face-to-face this fall. But before tonight's debate, Mr. Gingrich faced new and potentially damaging allegations from his second wife, who says in an interview with ABC News that Mr. Gingrich proposed an "open marriage" so that he could continue his affair with Callista Bisek, the woman who became his third wife. That interview, which ABC plans to show tonight after releasing portions during the day, will add to the baggage that Mr. Gingrich, a former speaker of the House, carries as he engages with Mr. Romney. Rivals have accused Mr. Gingrich of ethical violations while in office, earning more than $1 million representing the mortgage giant Freddie Mac, and opposing plans by Congressional Republicans to cut spending and reform Social Security. Jim Dyke, a veteran Republican consultant based in South Carolina, said Mr. Perry's decision to drop out would "feed a perception of momentum" by Mr. Gingrich. But he said the questions about Mr. Gingrich's record and past statements remained a serious challenge. "Gingrich will have to answer questions sooner or later, and there is still a lot to answer," Mr. Dyke said. Steve Schmidt, who helped run John McCain's presidential campaign in 2008, said Mr. Gingrich had benefited from the Republican Party's "final spasm of anti-Romney opposition," especially in South Carolina. "There's a lot of empirical evidence to suggest that Romney is losing altitude and that Gingrich is closing the race," Mr. Schmidt said. He said Mr. Gingrich had demonstrated resilience in his ability to recover from setbacks during the campaign. But Mr. Schmidt questioned whether Mr. Gingrich has demonstrated any other qualities to prove that he could be an effective challenger to Mr. Obama as the party's nominee. "The Gingrich candidacy could be a reality show in its own right, infused with melodrama and erratic swings," Mr Schmidt said. When you consider the prospects of a Gingrich nomination, the likelihood of an Obama re-election goes up dramatically. That argument is central to the case that Mr. Santorum is making as he seeks to capitalize on the odd turnabout in Iowa, in which party leaders there said he had finished slightly ahead of Mr. Romney in the caucuses, and on the endorsement he received last weekend by a group of evangelical leaders. After the updated results in Iowa were announced Thursday morning, Mr. Santorum's campaign spokesman sought to claim the mantle of the conservative alternative to Mr. Romney. "The narrative that Governor Romney and the media have been touting of "inevitability" has been destroyed," Hogan Gidley, Mr. Santorum's communications director, said in a statement. "There is a consistent conservative alternative" adding, "that candidate is Rick Santorum." Representative Ron Paul of Texas is also making that case, arguing in speeches and in advertising that his three remaining rivals are not true conservatives and have political baggage that will make it impossible for them to change the culture in Washington. But polls suggest that it is Mr. Gingrich - and not Mr. Santorum - who is making headway in the effort to persuade voters to choose someone other than Mr. Romney. An NBC/Marist poll released Thursday morning shows Mr. Romney with a 10-point lead over Mr. Gingrich, 34 percent to 24 percent. But the survey, which was taken over two days early this week, shows a closer race in interviews done after Monday evening's debate. The poll was also taken before Mr. Romney said he had paid an effective tax rate of about 15 percent, a disclosure that drew wide criticism. An adviser to the Romney campaign said its own internal polls showed a close race as voting nears. But the polls are not all good news for Mr. Gingrich. The CNN/Time survey and the NBC/Marist poll both show that Mr. Gingrich does significantly worse than Mr. Romney among women in South Carolina, a crucial group that could help determine the outcome of the race on Saturday. That gap in support among women could be exacerbated by the ABC interview, which is scheduled to be broadcast Thursday night after the debate. Mr. Gingrich has been married three times. His campaign dismissed the allegations from his second wife as old news and called it unfair for the story to run just before the primary. For Mr. Gingrich, another good debate performance Thursday night could help propel him to victory on Saturday. But he still faces long-term challenges, including a lack of money and a paltry campaign infrastructure in most parts of the country. Top strategists for Mr. Romney's campaign expressed confidence that he would withstand a surge by Mr. Gingrich, even if Mr. Gingrich ends up winning in South Carolina. They noted that months ago, political observers would have said it was a long-shot for Mr. Romney to win the state in the first place. Kevin Madden, an adviser to Mr. Romney, said Mr. Gingrich was benefiting from a Republican electorate that has been especially volatile. But he said Mr. Romney was still in a better position to win than Mr. Gingrich or any of his other rivals. "The Romney campaign has been built around a model that expects very close contests in all of these states," Mr. Madden said. The candidates are going to be judged on their ability to make the case that they are the best one to turn the economy around and which candidate is best positioned to beat Obama in the general election. In addition to the debate, that argument will be fiercely made in a final flurry of television ads that will blanket South Carolina airwaves through Saturday. But Mr. Perry's departure will silence one of the loudest guns in the fight: Make Us Great Again, the "super PAC" that once planned to spend $55 million to help Mr. Perry win the nomination. Officials at the group asked television stations in the state to cease running attack ads targeting Mr. Gingrich, according to a person involved with Make Us Great Again. The group had already spent most of its money, the person said, and would likely shut down in the coming days.