Feminism’s final frontier? Religion.

The battle of the sexes, waged this election season with fulsome fury in the public space, is being fought in a much more painful, private sphere as well. In churches (and synagogues and mosques) across the land, women are still treated as second-class citizens. And because women of faith are increasingly breadwinners, single moms and heads of households, that diminished status is beginning to rankle.

There are churches in America in which women aren’t allowed to speak out loud unless they get permission from a man first.

There are churches (many of them) in which women aren’t permitted to preach from the pulpit.

There are churches in America where a 13-year-old boy has more authority than his mother.

“At church I had to hide my thoughts, questions and life choices,” says Susan, a woman who works as a therapist in Seattle and, after a lifetime of following Jesus, left Christianity. “I didn’t think I could do anything by myself, because as a Christian woman I’d learned that I needed a man to get places.”

Susan’s story was published in January by a small Christian publishing house in the book “The Resignation of Eve.” In its pages, the author, an evangelical minister named Jim Henderson, argues that unless the male leaders of conservative Christian churches do some serious soul-searching — pronto — the women who have always sustained those churches with their time, sweat and cash will leave. In droves. And they won’t come back. Their children, traditionally brought to church by their mothers, will thus join the growing numbers of Americans who call themselves “un-churched.”

Nevermind that the Bible talks about women submitting to men and sitting silently in church, Henderson declaims. That’s ancient history.  “Until those with power (men) decide to give it away to those who lack it (women), I believe we will continue to misrepresent Jesus’ heart and mar the beauty of his Kingdom,” Henderson writes.

Henderson bolsters his argument with data from the Barna Research Group. Between 1991 and 2011, the number of adult women attending church weekly has declined 20 percent. The number of women going to Sunday school has dropped by about a third, as has the number of women who volunteer at church.

And although the Barna data have been disputed by other researchers, Henderson goes further. Even those women who go to church regularly, he says, are really only half there: Their discontent keeps them from engaging fully with the project of being Christian. He calls this malaise among women “a spiritual brain drain.”

I think of these faithful conservative females in this political season, struggling to make ends meet and keep their eyes on God as the men of the right, also known as “the patriarchy,” disrespect and insult them.

It is not only Rush Limbaugh who demeans all women by calling one a “slut” and a “prostitute.” It’s Rick Santorum — that man of faith — who has stopped just short of calling working mothers selfish and who lumps all single moms together as his opposition, as he did in an interview with Tony Perkins of the Family Research Council last year.

“They look to the government for help and therefore they’re going to vote,” Santorum said. “So if you want to reduce the Democratic advantage, what you want to do is build two-parent families.” It is every single policy that puts so-called “small government” ahead of the health, welfare and education of children.

I think of the bloggers on Feminist Mormon Housewives who insist on their devotion to the Church of Jesus Christ of Latter-day Saints while sensibly rebelling against teachings that make women inferior to men. I think of the women at the Jewish Orthodox Feminist Alliance, who, barred from leadership roles in synagogue, are starting small prayer groups of their own, where they can perform Jewish life-cycle rituals together.

I think of Kelly, a subject in Henderson’s book who, after making a case for women in ministry at her church, got the silent treatment from her pastor for months. Kelly left that church and started a group that met in people’s living rooms. There, she is a leader. “This is my church, and I love it,” she says. “It’s a community I cultivate and pastor.”

The political analogies are clear. According to a new NBC/Wall Street Journal poll, President Obama wins in any matchup against Mitt Romney, Santorum or Newt Gingrich. Among women, though, his gains are huge: 18 points, 24 points and 27 points, respectively. Unless the strident, authoritarian social conservatives loosen their stranglehold on American women, American women will abandon the Republican Party (as they’re quitting church) and look for their candidates elsewhere.