IN A YEAR when “Virginity Rules” became an abstinence movement motto, the pendulum swings to new rules for an open marriage. With recent statistics from 13 countries showing that marriage is down while living together is up — and monogamy being challenged by polyamory — will the words “for better or worse, until death do us part” become obsolete?

Polyamory means sharing more than one intimate partner at the same time. Unlike the ménage à trois or Updikean wife-swapping, polyamory is characterized by multiple-relationship arrangements with the consent of all partners and defined by specific boundaries.

But then, couples have been choosing alternative arrangements for years — look at Eleanor and Franklin D. Roosevelt (and his mistresses), Nelson Rockefeller and his mistresses, and the open relationship between John Lennon and Yoko Ono. In the 1800s, the married Amherst College treasurer, Austin Dickinson, spent 13 years involved with a young professor’s wife. In writing about their relationship, Mabel Loomis Todd proclaimed she could love two men at the same time. (Poet Emily Dickinson helped her brother and Mabel keep the affair alive.

One man loving three wives at the same time is depicted in Big Love, an HBO tale glamorizing polygamy. Since I do not own a television, I missed the 2006 debut and had to wait to read about marriage alternatives in two new books that are shedding light on sexual-preference-packages.

Written or unwritten rules that include mutual respect, agreements, and even contracts between various partners appear to set apart today’s open marriages from the swinging ’60s. Tristan Taormino, in Opening Up: A Guide to Creating and Sustaining Open Relationships, describes a variety of arrangements, including monogamy with benefits, triad couples and solo polyamory. The resource list of polyamorous groups is broken down by state and country.

Taormino says her goal is “to empower people to let go of societal expectations of what relationships should look like and create customized relationships that meet their needs and desires.”

Jenny Block’s Open: Love, Sex, and Life in an Open Marriage is a memoir. She wrote me and said, “I do think that polyamory might well work for many people. That’s not to say that I have any problem with monogamy. I think it is great when a couple is actually practicing it and not just giving lip-service to the concept.”

However, as a Rhode Island hairstylist of 20 years, Cindy Gouveia, says: “I hear an awful lot from people. If you have to go outside of your marriage, you cannot be in a truly happy marriage. Who is kidding who?”

Escalating marital infidelity and divorce rates may be contributing to the rise in cohabitation. A young couple from Portland, Ore., visiting family members in Barrington, expressed a growing sentiment. Amanda Thibodeau said: “Marriage is a government and legal institution, and we have lost faith in both. Why do I need these institutions telling me that my relationship is official?”

Of their relationship Scott Beck added: “We are working on being good partners for each other, like other couples who are married or not, gay or straight, young and old. I also see living together as a sacred ritual where two people can publicly make a commitment to caring for each other . . . even if you’re pagan anarchists.”

Ironically in an era when many are giving a “thumbs down” to marriage, gay couples are still lobbying for the right to marry.

What message do marriage alternatives give to young people? In the absence of role models, we are spending taxpayer dollars for abstinence programs that congressional-funded research shows are failing. Why not spend money on family-focused education that includes conflict resolution, financial management, sexual responsibility and child care? We might even consider courses that talk about intimacy and love as a choice rather than wild infatuation.

Perhaps it is time for a return to experiments in which students are graded on taking care of “flour sack babies.” This might make planned teenage pregnancies, as recently seen in a Gloucester, Mass., high school, less attractive.

Does marriage even have a future? As an incurable romantic, I am ever hopeful. But I paused at a recent New Yorker cartoon by Michael Crawford. A middle-aged couple in the formal “just married” attire of tux and tulle are sitting in the back of a limousine. The caption reads: “It didn’t have to end like this.”

Rita Watson is a monthly contributor and daily blogger at www.ritawatson.com who writes about relationships.