The nation's mainline Protestant denominations have quarreled for years over the role of gays and lesbians in church life, but those debates promise to grow even more intense and acrimonious this summer.
The conflicts, which come as several states wage legal fights over gay marriage, could well influence whether some of the religious denominations remain intact or splinter into smaller factions.
California's Supreme Court is expected to rule Tuesday on the constitutionality of the state's ban on same-sex marriage. For the faithful in a number of American churches, the legal battle over civil marriage for gay and lesbian couples runs parallel to religious struggles that are strikingly similar and often just as heated.
One of the most visible denominational skirmishes will occur in July, when leaders of the 2.2-million-member Episcopal Church consider proposals at their national convention to sanction a religious rite for blessing same-sex unions and ease restrictions on the ordination of gay and lesbian bishops.
If approved, the steps could further alienate theological conservatives, giving them reason to join four Episcopal dioceses and hundreds of parishes that split away in 2008 to form a separate church.
The country's largest Lutheran denomination, meanwhile, is scheduled in August to consider a long-anticipated statement on human sexuality that among various elements says that Christian tradition recognizes marriage as a covenant between a man and a woman.
Even as they acknowledge deep divisions over homosexuality, members of the 4.7-million member Evangelical Lutheran Church in America will decide at their meeting whether they should enable local congregations to recognize same-gender unions and allow "practicing homosexuals" in committed relationships to serve in ministry.
Other Protestant groups are embroiled in similar struggles, including the Presbyterian Church (USA) and the United Methodist Church. Another, the American Baptist Churches USA, is scheduled to hold its biennial convention in June but is not expected to consider any action related to gay marriage, a spokeswoman said.
But scholars are watching Episcopalians and Evangelical Lutherans closely, seeing them as a gauge for other denominations. The experts are waiting to see if the intensified debate and turmoil leading up to the national conventions produce any consensus on issues that have long divided U.S. Protestants.
"What has been emerging for the last several years is becoming even clearer now: We're on a trajectory toward the blessing of same-sex unions and the ordination of lesbian, gay, bisexual and transgender people," said the Rev. Jay Johnson, a professor of theology at the Pacific School of Religion in Berkeley, Calif., and director of academic research at its Center for Lesbian and Gay Studies in Religion and Ministry.
But Johnson added: "It may mean, when there are breakthroughs in these churches, we see more breakaways."
U.S. Christians remain stubbornly split over homosexuality. One recent survey by the Pew Forum on Religion & Public Life found that 56 percent of mainline Protestants believe it should be accepted by society. Just 26 percent of Evangelical Protestants felt that way.
Few denominations have been as torn by the issue as the Episcopal Church, the U.S. branch of the Anglican Communion, a 77-million-member fellowship. Theological conservatives are a minority in the Episcopal Church but a large majority among Anglicans worldwide.
The conflict between church liberals and conservatives escalated in 2003 with the consecration of an openly gay priest, the Rev. V. Gene Robinson, as bishop of New Hampshire. Amid pressure from traditionalists within the U.S. church and Anglicans officials elsewhere, Episcopal leaders agreed at their last General Convention in 2006 to urge local church authorities not to consecrate any bishop "whose manner of life presents a challenge to the wider church."
Still, 700 conservative parishes in the United States and Canada defected in 2008 and formed a new church affiliated with overseas Anglicans.
Now, as Episcopalians approach their July convention in Anaheim, Calif., dioceses are submitting resolutions to ease restrictions on gay bishops and to authorize same-sex marriage blessings. The issue of blessings is now left up to local Episcopal authorities.
The convention's host, the Episcopal Diocese of Los Angeles, has tried to send a message of its own by approving a policy at its December convention that gives local priests permission to officiate at rites of blessing for gay or lesbian couples.
"I think it's about time we get about the business of having marriage equality in the church," said the Rt. Rev. J. Jon Bruno, bishop of the Los Angeles diocese. "I am waiting with baited breath to see what happens" at the Anaheim meeting.
Conservative Episcopalians argue that liberalized policies not only will alienate U.S. parishes but add further strain to the church's already troubled relationship with church leaders in Africa and elsewhere in the global Anglican Communion.
In May, , one of the communion's worldwide leadership bodies affirmed its support for moratoriums on consecrating noncelibate gay bishops and on blessings for same-sex couples. The group was led by Archbishop of Canterbury Rowan Williams, the communion's spiritual leader, who is scheduled to attend the Anaheim convention.
Resisting those mandates will "turn up the flame," said the Rt. Rev. Edward S. Little II, bishop of the Diocese of Northern Indiana and a leader in a group of clergy trying to strengthen Episcopal ties to the Anglican Communion. "If we take a step at General Convention that takes us down the road, we will lose more people," he said.
Still, the Episcopal Church's presiding bishop, the Most Rev. Katharine Jefferts Schori, said she believes the U.S. church and its global partners can co-exist even if they disagree on the rights of gays and lesbians in the church.
"We're not afraid of people watching over our shoulders," Jefferts Schori said. "We live with diversity on issues that get people charged up."
Evangelical Lutherans are weathering an equally emotional debate as they prepare for their Churchwide Assembly in Minneapolis, a gathering that many predict will expose deep divisions over homosexuality and biblical authority.
Denomination leaders will vote on a lengthy social statement -- "Human Sexuality: Gift and Trust" -- that has been eight years in the making and identifies marriage as a union between a man and a woman. Such statements are intended to guide church members in setting policy and forming judgments about social issues, officials have said.
Lutheran leaders also will consider a policy that asks whether the church "should commit itself" to find ways to allow local congregations, if they choose, to recognize "life-long, monogamous, same-gender relationships."
Another policy asks whether the church should find a way to allow gay people to serve in ordained positions. Current Lutheran policy bars "practicing homosexuals" from ministry.
Lutherans Concerned-North America, a gay-rights group, praised the sexuality paper for extolling the importance of committed relationships but criticized it for failing to include a marriage blessing for same-sex couples.
"We have ... a blessing of liturgical furnishings, including chairs and kneelers. Surely we can find our way clear to have a rite of blessing for two people, good Christians, who wish to commit themselves to each other until death do they part," said Phil Soucy, a spokesman for the group.
Conservatives, meanwhile, argue that any such shift in policy will alter fundamental biblical teachings about homosexuality. A coalition of Evangelical Lutheran members and congregations issued a letter last week to voting members of the upcoming Churchwide Assembly meeting, urging them to defeat proposals they believe would put the denomination at odds with fellow Lutherans in Asia and Africa.
"There are going to be some congregations that leave," said the Rev. Mark Chavez of the Lutheran Coalition for Reform, a group that supports traditional Lutheran positions on marriage and other issues.
(Optional add end)
The church's presiding bishop, Mark S. Hanson, said he believes the Evangelical Lutheran tent can accommodate a spectrum of views, even as he laments that the ongoing debate has obscured the other works of the church and the common faith shared by Lutherans.
"I'm not naive about the possibilities that those who do not support the decisions will find it difficult to stay in this church body, but I'm committed that we will engage one another ... ," Hanson said. "I don't think the diversity we're experiencing is a problem to be solved. Diversity is a gift of God, just as unity is a gift of God."