Newt Gingrich's Saturday win over Mitt Romney in the South Carolina presidential primary is being lauded by the National Organization for Marriage (NOM), the nation's most vociferous opponent of gay marriage.

Gingrich finished with 40.4 percent of the South Carolina vote, far ahead of second-place finisher Mitt Romney, who received 27.8 percent of the vote. Rick Santorum came in third (17%) and Ron Paul (13%) fourth.

The former speaker of the House turned a last-minute political liability – allegations by his ex-wife that he had asked her for an open marriage – into an asset when he attacked the media for running the story.

“NOM congratulates Newt Gingrich on his impressive come-from-behind victory in South Carolina,” said NOM President Brian Brown. “We have had three different victors in state contests thus far – Rick Santorum in Iowa, Mitt Romney in New Hampshire and now Newt Gingrich in South Carolina. What all these states have in common is that they have picked candidates who have signed NOM's Marriage Pledge. They are all winners and NOM supports each of them.”

Texas Rep. Ron Paul is the only candidate remaining in the race who refused to sign the group's anti-gay marriage pledge.

Candidates who sign NOM's 5-point pledge promise to support a federal constitutional amendment banning gay marriage, defend the Defense of Marriage Act (DOMA) in court, appoint judges and an attorney general who will “respect the original meaning of the Constitution,” appoint a presidential commission to investigate the “harassment of traditional marriage supporters,” and back legislation that would allow a ballot question on the issue for voters of the District of Columbia.

NOM called Paul wrong on marriage for deciding not to sign the document and launched an ad attacking him on the issue. (The video is embedded in the right panel of this page. Visit our video library for more videos.)

“Paul is the only remaining Republican presidential candidate not to have signed the pledge, and he is not considered to have any realistic chance of becoming the Republican nominee,” the group said in a statement.

“It is now clear that the Republican Party will nominate a candidate who is strongly committed to preserving marriage as the union of one man and one woman,” Brown added. “We have succeeded in making the preservation of marriage a key issue in this race, and we will continue to do so throughout the primary season, and into the general election against President Obama.”