In her decades of researching polygamy, Janet Bennion, a professor of anthropology and sociology at Lyndon State College, recalls three times she was “courted” by married women. One wrote her “love letters.” Another took her to a restaurant “to determine whether I was wifely material,” Bennion writes in her new book, Polygamy in Primetime.

These women were devout members of fundamentalist Mormon sects, not swingers. Like many examples in Bennion’s illuminating study, they defy the popular perception that the practice of men taking multiple wives is solely about the male libido.

Liberal Vermonters have cheered on the progress of marriage rights this election season. But what would we say to a woman who sought to unite herself in matrimony to a man and another woman?

We might crack jokes about group sex, accept such a union as “polyamory,” or view it as dangerous to women’s rights when associated with a patriarchal religion. But whatever we think of polygamy in America, Bennion argues, it’s not going away anytime soon. And she believes it should be legal.

Bennion, 48, has been researching polygamy for two decades. As a master’s student in 1989, she moved in with a rural Montana colony of the Apostolic United Brethren, a fundamentalist Mormon sect that still practices plural marriage as instructed by founder Joseph Smith in 1843. (The Church of Jesus Christ of Latter-Day Saints [LDS] officially renounced polygamy in 1890.)

Bennion would go on to publish book-length ethnographic studies of the AUB and the LeBaron fundamentalist colony in Mexico. Her fieldwork got her in trouble with LDS church leaders, who “disfellowshipped” her. And she writes candidly in the introduction to Polygamy in Primetime that it also didn’t do wonders for her relationship with her first husband (“living with polygamists is not good for a healthy marriage!”).

But she made new friendships with a startling range of polygamous women. Most bore little resemblance to the underage brides in prairie dresses familiar from news reports about raids on Warren Jeffs’ Fundamentalist Church of Jesus Christ of Latter-Day Saints (FLDS). Women in the large AUB group can and do work outside the home, dress as they choose and divorce when they wish.

Take Elizabeth Joseph, a journalist and lawyer who “relied on her co-wives to help her with child care and meal preparation.” Or the three suburban wives of Rod Williams who shared childcare duties so one could earn a business degree while another got her master’s in sociology. Or the women who, Bennion writes, “would often say to me that they felt sorry for monogamous women who were with their husbands all the time.”

Such modern-style American polygamist families kept a low profile until recently, when two TV shows — HBO’s “Big Love” and its reality-show counterpart, TLC’s “Sister Wives” — put them in the spotlight. Meanwhile, in 2010, a Canadian court case posed a landmark challenge to that nation’s anti-polygamy law (which was upheld in November 2011).

Polygamy in Primetime responds to this new visibility with an overview of the subject that, despite occasional academic language, will appeal to general readers seeking more details than the soap operatics of “Big Love” can provide. Bennion argues provocatively that, just as marriage-equality legislation followed the advent of nuanced media portrayals of gays and lesbians, so “the decriminalization of polygamy will follow the recent poly media phenomenon.”

Of course, there are plenty of reasons for progressives to question the notion that polygamy is part of the “new American sexual revolution,” as Bennion puts it. Mormon plural marriage is tied to patriarchy and the official subordination of women who have access to the privileges of “priesthood” only through men (as in mainstream LDS). The practice rests on the assumption that all fertile women should be breeding; it relies on a high female-to-male ratio; and it has led to abuses, from the rape of teenagers to the mass expulsion of young men who threatened the ruling patriarchs’ monopoly on nubile wives.

But, as Bennion points out, monogamy has sheltered abuses, too. Polygamy, she believes, will never be “the prevalent marriage structure.” Yet it seems to work for some, including mainstream LDS women who convert to fundamentalist sects seeking a “good man” they can’t find in the regular dating pool — even if they have to share him.

We may assume we know why men opt for polygamy: Is a guy who maintains three wives in connected households really that different from a secular serial monogamist on his third or fourth family? But why would an educated, independent-minded woman choose such a situation?

Bennion is happy to chat about such questions from her office at LSC, where she’s taught for the past 10 years. Her previous job was at Utah Valley University, where the high birth rate led to “enormous” classes, she says. Her two daughters are graduating from the University of Vermont, and Bennion says she wouldn’t want plural marriage for them — or for herself. But the anthropologist, who calls herself a “gender humanist,” is fascinated by the “ways that women find surprising ascendancies, empowerments, autonomy” within fundamentalist cultures, she says.

SEVEN DAYS: What do women find in polygamy?

JANET BENNION: One reason I wrote this book was to underscore the variability in experience for women in these groups. If you’re in the FLDS, you’re going to find more restrictions, but even there, some women are able to find ways around them. The Allreds [AUB] have been able to provide women with more venues for power, such as hypergamy, or divorcing a husband and marrying up. The groups vary, and some women find that working with other women in the home is beneficial to them. One woman described her co-wives as “second mothers,” [who do the childcare] so she can go find a job in the community. They have this economical and social network that provides a little bit more freedom than you might see in a monogamous pair bond.

I’ve taken so many surveys in my classes, asking students, “Which parent in your home does the household work?” Eighty-five percent of students say, “Mom does it.” So that second shift is hard on the monogamous woman.

SD: What’s the relationship between fundamentalists and the LDS church?

JB: The mainstream [church] obviously does not recognize [polygamy] as a valid form anymore. Still, the mainstream is made up of people with ancestors who were polygamists. [Both Bennion and Mitt Romney have direct forebears who were persecuted or prosecuted for polygamy.] You can see that there are some sensitivities there, especially in an election year. Half of my family was for Romney, the other half for Obama. The Romney half was saying, “You shouldn’t have that book out there.”

The Mormon church today is very mainstream. It’s changed many of its doctrines to fit an evolving constituency, but the priesthood is still firmly in the male corner. If you’re connected to the Mormon community and you’re a liberal woman like me, you live for the day when women can have the priesthood. Allred women use the priesthood covertly to bless the children. They actually have some informal venues that give them more power than the monogamous mainstream woman.

SD: You mention having a “theory that plural marriage fosters clandestine lesbianism” — something the LDS church doesn’t condone.

JB: That’s a new area of interest. I think women do what they need to do without a man around. Mormon women have done this for ages. There are women in the Utah pioneer days who formed a sisterhood network and allowed for lesbian connections. It doesn’t upset the patriarchal framework. I talked to at least three women who had formed sexual connections to their sister wives or to another woman in the community. When the husbands found out, they just called it a friendship. But for two men to get together — that threatens the hypermasculine roles that are the foundation for patriarchy.

SD: Were you ever tempted by polygamy?

JB: I was tempted to leave my husband, but I wasn’t tempted to join polygamy. I grew to love the women. Yet there was never that urge [to join them], ’cause I knew that I could never tolerate patriarchy, ever. I believe in all the nonpatriarchal components of Mormonism, but everything that deals with patriarchy, I put it out of my life.

SD: Why should we legalize plural marriage?

JB: We need to just step back, get off our high horse, and look at this from a civil liberties perspective. If we’re going to pave the way for alternative sexuality, why not provide liberties for those who choose the polygamy form? We hear a lot about the abuse cases, but we rarely hear about the well-functioning families. As a feminist, I say, “Bring it on; let’s legalize it.” In that way, what you do is you bring the abuses into the light. You bring in governmental regulating policies that protect second wives.

[This position is] controversial, that’s for sure. There are abuses, but to state that polygamy is uniformly abusive is just an outright lie. It’s a form of bigotry.

SD: Given the reasons you cite for modern single women to choose polygamy — access to high-status men, emotional and economic support from co-wives — is it likely to start taking nonreligious forms?

JB: I think there actually are these kinds of families but they are the outliers. Because polygamy is such a hard lifestyle, you have to have some cultural basis for living it. When you sit there thinking about your husband having sex with your sister wives, you have to have some sort of ideology.

It doesn’t have to be Mormon. Among African-American Muslims and converts who are professional women in Detroit and Chicago and other areas, you’re going to find women actually opting for this form. Islam allows for four wives for each man, so there’s an ideological framework. They want to opt for a better man, and they’d rather share a good man with another woman than be unmarried without the possibility of having children.

I’m finding also a rationale for polyandry. I had an angry man call me recently, and he said, “I’m angry at the polygamists because they’re hoarding all the women.” There are a lot of men who might at this point be interested in the alpha female. We’re opening up to new and creative sexual forms in order to deal with our socioeconomic crisis. So stay tuned.

"Polygamy in Primetime: Media, Gender, and Politics in Mormon Fundamentalism" by Janet Bennion, Brandeis University Press, 376 pages. $35.