The idea of trying a nonmonogamous marriage by mutual consent enjoyed a brief cultural vogue, along with encounter groups and key parties, after the publication of the best-selling book “Open Marriage: A New Life Style for Couples,” by Nena and George O’Neill, in 1972. But once the AIDS epidemic hit, talk of open marriage seemed to vanish in polite circles. “The 1980s and much of the 1990s saw an almost complete eradication of the term ‘open marriage’ from public discourse,” said Dr. Curtis R. Bergstrand, an associate professor of sociology at Bellarmine University in Louisville, Ky., who recently wrote a book on the practice. Even to evoke the term nowadays sounds, to many, a little dated, like referring to your wife as your “lady” or to a band as a “group.” But like Mr. Gingrich himself, the concept has popped up again, and not just as an unlikely topic in primary-season discourse. The phrase has become a titillating staple of celebrity gossip headlines. And the idea of the open relationship, supported by Web sites and a new generation of books, is showing signs of a second life as an alternative-sexual subculture for a generation acclimated to high divorce rates, Dr. Bergstrand said. Many are latchkey children of the Generation X-cliché variety who grew up after the sexual revolution, when divorce had become routine and alternative sexual options, beats by dre solo like bisexuality, have become more socially accepted. If nothing else, Marianne Gingrich’s allegation, which the candidate has denied, provided an unexpected publicity bounce for advocates cheap beats by dre studio of open relationships, who have long been trying to paw their way out of the cultural margins. “We could never afford this kind of a public-relations opportunity,” said Anita Wagner Illig, an organizer of the Polyamory Leadership Network, an online organization advocating nonmonogamous relationships. She was interviewed by the BBC and Washington’s ABC news affiliate after the statements by Marianne Gingrich, and traffic at ModernPoly.com, an advocacy Web site promoting open relationships, spiked nearly 30 percent in the weeks that followed. Though Mr. Gingrich’s candidacy unintentionally helped reintroduce the topic of open marriages in mainstream conversation, no one in the subculture appears to be embracing him as a celebrity spokesman. As Ms. Gingrich told reporters, her ex-husband asked for an open marriage, though not in those exact words, after a counseling session so he could continue to see another woman, Callista Bisek, to whom he is now married (a story Mr. Gingrich angrily refuted). Advocates go to great pains to dispel the idea that open marriage, at least when practiced responsibly, is just a handy after-the-fact excuse for wandering spouses. “Cheating while married can technically fall under polyamory since it does mean ‘many loves,’ ” said Birgitte Philippides, a New York makeup artist and former president of Polyamorous NYC. “However, people in the polyamory movement don’t usually like to look at it that way. They think cheating is just cheating.” As Blogs » The-MIC practiced today, open-marriage arrangements can take many forms. Some fall under the rubric of polyamory, which involves a couple sharing emotional and romantic attachment, as well as sexual, with more than one person. (Not all polyamorists are married, however, and many relationships involve bisexuality.) Some fall under the term “partnered nonmonogamy,” which involves outside sexual relationships, but no emotional attachment, said Tristan Taormino, the author of “Opening Up,” a 2008 survey of 100 nonmonogamous relationships in this country that includes advice on managing jealousy and parenting duties for latter-day Bobs and Carols and Teds and Alices. Despite the whiff of Roman-scale hedonism, modern open marriages often have little to do with the swinging sex romps of the “Love the One You’re With” era. Ground rules are usually settled on in advance by all parties. Some even sign family contracts delineating financial obligations, said Diana Adams, a New York lawyer and practicing polyamorist. Others seek to lend the practice an air of legitimacy by using terminology like the lawyerly “negotiated monogamy.”