Cushman says her father developed an early sense of duty, an almost militant commitment to the United States. “He came from a broken home and his stepfather adopted him,” she says. “They moved around a lot, to bases in Kansas, France, Germany. With an infantry officer as his dad, believe me, they were not singing ‘Kumbaya’ in that house. It was about service, and he had a revelation at the Verdun battlefield. Visiting there as a teenager, he felt called to serve.”

Many decades later, Cushman says, Gingrich “truly believes that this presidential campaign, and politics, is his service to his country.” Quietly bowing out, simply to return to private life, would be out of character. “This is not some personal vendetta,” she says. “You volunteer to run for president. No one forces you to do it. This is what he feels he is supposed to be doing. I’m sure the Romney people would love for him to drop out, but it’s not going to happen. He’s got that infantry mentality — he’ll keep trudging ahead.”

For the most part, Gingrich’s advisers agree, telling me that a return to political winter — even if it means more speaking gigs and a hefty television contract — is something Gingrich wants to avoid. “He has lived that life already, doing Fox News and consulting,” says one source. “At his age, he is in no rush to get back to that kind of thing. He sees Romney flailing in Minnesota and sees more than enough reason to think that he can come back and win the nomination. In a head-to-head match against Romney, he thinks he wins. And he does not think that Santorum will be able to withstand the Romney attacks that will come.”…

Longtime Gingrich watchers cite another factor for his refusal to quit: His place in the history books. They respect that he may find the odds of winning if he remains in the race appealing. But they caution that encouraging poll numbers in certain states are not the only impetus for his obstinacy. Even if he loses, “he becomes the classic insurgent,” says Frank Gregorsky, Gingrich’s former chief of staff, who is writing a history of House Republicans. “More than Eugene McCarthy or Gary Hart, or others like them, he has emerged as a self-righteous guerrilla fighter.”