As the church suddenly faces an unexpected transition, American Catholicism is shrinking in size and splitting into two often harshly opposing camps — growing more polarized in faith, just as the nation has divided itself politically and socially.
The sexual abuse scandals that have rocked the U.S. church, along with its hard-line stands on celibate priests, homosexuality and ordaining women, have pushed many Americans away from the church, which is still the nation’s largest single denomination.

The prospect of a new pope provides a new focus for the world’s fourth-largest Catholic population, as Americans ask whether Catholicism will grow smaller but hew to traditional doctrine or follow its members as they adapt to a fast-changing society.

The latest surveys of American Catholics reveal sharp drops in weekly Mass attendance, a majority in support of legalizing same-sex marriage, and a large majority who say they do not look to the Vatican as the moral authority on sexual matters such as contraception, marriage and abortion, said William D’Antonio, a sociologist at Catholic University in Washington and author of a national survey that has tracked Catholic attitudes for 25 years.

“The laity are saying, ‘We can work things out for ourselves, these are matters for our own conscience, not questions where we just follow what the church is demanding,’ ” he said.

Just as Americans are now deeply divided over the role of government, Catholics have cleaved into two camps, one in which their religion is defined by its core tenets, the sacraments and concern for the poor, and another in which the church’s authority on the most personal aspects of life remains clear and essential, according to D’Antonio’s survey.

Hardly a week goes by without someone asking Elizabeth Scalia why she is still a Catholic. She has never felt a need to step away from her church, but the growing rift between American Catholics and their faith has forced her to a conclusion she once considered sad: The Catholic Church will and should become smaller, perhaps much smaller.

Scalia, like many traditional and conservative Catholics, says the experience of recent decades, as more Catholics have become more casual adherents to their faith, proves that the church should stick to its guns and accept that its beliefs may attract fewer people — and yet become more meaningful and effective.

“The world has gone superficial and promiscuous and morally avaricious, and the church is standing against that,” said Scalia, 54, of Long Island, a Catholic writer and Benedictine oblate — a lay person dedicated to religious life. “Do we want a large church of people who aren’t paying attention, or a smaller church of people who are fervently attempting to be the faith that can heal the world? Who wants a church of people who don’t care? I wouldn’t want to be on a softball team of people who don’t care.”

But John Gehring, a churchgoing Catholic who works at Faith in Public Life, a liberal advocacy group in the District, says the only hope the church has of stemming the tide of disengaged American Catholics is for the hierarchy to “stop being the Church of No and once again put it at the forefront of social justice and helping the poor.”

“When being a good Catholic is defined on a narrow range of sexuality issues rather than a more positive, loving vision, it’s no wonder people are moving away,” said Gehring, 38. “For me personally, my relationship with my faith has been to engage critically, and for that, I’m told I’m a bad Catholic. Well, I’m not going anywhere, but there’s a real sense of sadness that my church acts as if Catholics were this embattled, persecuted minority.”

With 74 million adherents, Catholics make up 24 percent of the U.S. population and have been the country’s largest Christian group since the late 19th century. More Catholics live in the United States than in all but three other countries (Brazil, Mexico and the Philippines).

But American Catholics today are strikingly different from their profile of even just 25 years ago. In 1987, for example, more than six in 10 Catholics were married. By 2011, that had dropped to just over half, with an additional 10 percent living with a partner outside of marriage. Catholics have moved into the middle class and beyond; the portion who have finished college has soared by 50 percent in just 25 years, to 27 percent.

Nathan Gagnon, 29, a practicing Catholic in Gaithersburg, Md., watched as his parents divorced, contrary to church teachings. Now, he believes clergy should be more accepting of modern marital strains. “When a couple does feel frustrated,” he said, they shouldn’t have to fear being “scorned” by a priest.

But Maria Theresa Garrison, 73, a native of the Philippines who came to the United States about 35 years ago, said that “if your faith changes, there is no faith. If you have to move according to what the new generations say or what the politics say, where is the faith?”

Garrison, who attends Mass daily in Falls Church, said that she has watched nieces and nephews move away from the church because of issues such as abortion and same-sex marriage, but that the church should stand by its principles. “Today the message is that man is first, that the world has changed and our views should change, too,” she said. “But if your faith is in God, you put God first.”

For Blanca Portillo, 21, a resident of Falls Church, Va., who attends St. Anthony of Padua Church, the church’s tone has been too harsh: “Instead of fighting and telling people, ‘Don’t do abortion, abortion kills,’ just help the person,” she said. “I am not saying the Catholic Church should say it is okay to do abortions, but . . . I think the church, its main duty is trying to tell people the why rather than impose rules.”

Cardinal Donald Wuerl, the archbishop of Washington, on Monday reiterated Pope Benedict XVI’s recent reminder that “there is a basic doctrine that is bedrock for Catholic faith. So I suspect that every pope is always going to be conscious of the need to proclaim the received tradition of the church. And then the challenge is living with that and applying that to the moment, to the circumstances of our day.”

Demographically, the U.S. church’s flock has shifted markedly, with non-Hispanic whites falling from 86 percent of Catholics in 1987 to 63 percent in 2011. Nearly all of the growth has been among Hispanics, who went from 10 percent of the Catholic population to 32 percent over that same period, according to Catholics in America, a survey conducted for the National Catholic Reporter.

The Rev. Jose Eugenio Hoyos, director of the Spanish Catholic Apostolate of the Diocese of Arlington, Va., and a native of Colombia, said the recent emphasis on transparency and helping those who have been abused has positioned the church for an American pope.

“This is an opportunity for us Catholics to demand a pope with origins in the United States or Latin America,” he said. “Just like in the United States we now have an African American president, the church also needs a change. We need a pope who is ours, a pope who speaks about pupusas, about tacos, about horchata.”

Luz Lazo and Annys Shin contributed to this report.