Story highlights Newt Gingrich says "the story is false" and he's "appalled" it came up at a debate

Gingrich's second ex-wife speaks to reporters ahead of South Carolina's GOP primary

Gingrich delivered a family values speech a day after asking for open marriage, ex-wife says

His two daughters defend their father from their ex-stepmom's comments

Newt Gingrich offered his second wife a choice of an open marriage or a divorce when he revealed to her he was having an affair with the woman he later made his third wife, Marianne Gingrich said in interviews with ABC News and The Washington Post.

A day after he told his wife about his affair with Callista Bisek in May 1999, the former House speaker delivered a speech titled " The Demise of American Culture " to a group of Republican women in Pennsylvania, The Washington Post reported Thursday.

"How could he ask me for a divorce on Monday and within 48 hours give a speech on family values and talk about how people treat people?" Marianne Gingrich said in her interview with the Post.

The former congressman responded forcefully to the allegations at the start of Thursday's Republican presidential debate moderated by CNN, calling the story "despicable" and saying he was "appalled that you would begin a presidential debate with a topic like that."

"The story is false," Newt Gingrich said. "Every personal friend I have who knew us in that period said that story was false. We offered several of them to ABC to prove it was false, (but) they weren't interested because they would like to attack any Republican."

Marianne Gingrich's revelations echo what she told a reporter for an article published in Esquire magazine in August 2010 , but it is the first time Marianne Gingrich has talked about it on camera.

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"I said to him, 'Newt, we've been married a long time,' and he said, 'Yes, but you want me all to yourself. Callista doesn't care what I do,'" Marianne Gingrich said in the clip released by ABC, describing the couple's conversation near the end of their 18-year marriage.

Her husband, who had already left Congress, was asking "that I accept the fact that he has somebody else in his life," Marianne Gingrich said.

"Oh, he was asking to have an open marriage and I refused," she said.

She said she rejected his suggestion that they remain married while he keeps a mistress.

"No, no, that is not a marriage," she said.

The Esquire article reported that Gingrich asked his wife "to just tolerate the affair."

Newt Gingrich's marital history is not a new controversy for the Republican presidential candidate. He married Marianne Gingrich, who was a 28-year-old congressional staffer, six months after his divorce from his first wife, Jackie Gingrich, was final.

His presidential campaign has tried to frame the first divorce as something his then-wife wanted, contrary to court documents that indicated she objected to his divorce filing.

Jackie Gingrich has never talked on camera about her marriage. She refused a CNN request for an interview last month.

Newt Gingrich was asked about the controversy Thursday morning while campaigning in Beaufort, South Carolina, where voters will cast ballots in the GOP primary Saturday.

"It is an issue that I confront every time it comes up and I confront it exactly the same way every time it comes up and people seem to be satisfied with it," Gingrich said.

When pressed by reporters for a reaction to his second wife's TV interview, he said that his two daughters had "already written to ABC complaining about this as tawdry and inappropriate."

"Both of my daughters are prepared to speak on the record with any of you who would like to talk to them. Several other people who knew the situation are prepared to speak on the record. I am not getting involved," the former House speaker said, hours before the debate.

The letter to ABC from his daughters from his first marriage, Kathy Lubbers and Jackie Cushman, was released by the Gingrich campaign Wednesday.

"The failure of a marriage is a terrible and emotional experience for everyone involved," they wrote. "Anyone who has had that experience understands it is a personal tragedy filled with regrets, and sometimes differing memories of events. We will not say anything negative about our father's ex-wife. He has said before, privately and publicly, that he regrets any pain he may have caused in the past to people he loves."

The Gingrich daughters wrote that they were confident South Carolina voters were more interested in what their father has to say "about job creation, lower taxes, and about who can defeat Barack Obama by providing the sharpest contrast to his damaging, extreme liberalism."

"Our father is running for president because of his grandchildren -- so they can inherit the America he loves," they wrote. "To do that, President Obama must be defeated. And as the only candidate in the race, including Obama, who has actually helped balance the national budget, create jobs, reform welfare, and cut taxes and spending, Newt felt compelled to run -- to serve his country and safeguard his grandchildren's future."