By Peter Smith / Pittsburgh Post-Gazette

The Presbyterian Church (U.S.A.) is on track to rewrite the definition of marriage in its constitution by allowing it to include same-sex couples.

More than 40 percent of presbyteries, or regional governing bodies, have voted on the change as of Friday. While there's no official count yet, advocacy groups on both sides put the vote at 51 presbyteries in favor of allowing gay marriage and 23 against. Voting continues into the spring, with a majority of the 172 presbyteries needed for ratification.

The presbyteries are voting on a constitutional change endorsed in June by the denomination's General Assembly in Detroit. It would define marriage as a “unique commitment between two people” rather than specifically between a “man and a woman.”

While some denominations allow for same-sex unions or local discretion in responding to requests for same-sex weddings, the Louisville, Ky.-based Presbyterian Church (U.S.A.) would become the largest to write the change into its governing documents.

The effect would be somewhat anti-climactic in states such as Pennsylvania, because the Detroit assembly also authorized pastors to preside at same-sex weddings in jurisdictions where they are legal. That measure didn't require presbytery ratification.

Both measures also give pastors and churches the option not to participate in same-sex marriages.

The vote especially reverberates in the Tri-State area with its significant concentration of Presbyterians. More than 87,000 people are members of the Presbyterian Church (U.S.A.) in seven presbyteries in and around Pittsburgh.

The Pittsburgh Presbytery hasn't voted yet, but several area presbyteries have voted against redefining marriage, including Beaver-Butler, Shenango, Kiskiminetas and Redstone in Pennsylvania as well as Upper Ohio Valley in West Virginia and Ohio. Results are mixed elsewhere in Pennsylvania.

“I was certain this day would come sooner or later,” said the Rev. Janet Edwards, a Presbyterian minister from Pittsburgh and longtime advocate for same-sex marriages who was acquitted in a church trial in 2008 for presiding at such a marriage. “I think the reason it has come sooner is because of the fantastic love of lesbian and gay couples. We see in these couples such a commitment to each other, which we all recognize as marriage.”

Scores of churches, many in this region, have joined more conservative Presbyterian denominations in response to liberal trends in sexuality and theology in the Presbyterian Church (U.S.A.). That has compounded the denomination's chronic losses in membership. Membership stands at 1.8 million.

Some churches opposing same-sex marriage are staying put in the denomination, however.

“I'm very disappointed the church is going this direction” toward same-sex marriage, said the Rev. Paul Detterman, national director of the Fellowship Community, which includes more than 200 such churches. “I feel and continue to feel this is contrary to clear teaching of Scripture, but I also have a very clear sense of call to be speaking that conviction compassionately from within.”

Among the Fellowship Community churches is the historic First Presbyterian Church of Pittsburgh.

“The Presbyterian Church has a long history of splits and reunifications,” said the Rev. Tom Hall, senior pastor.

“When you take the long view … over time the issues tend to work themselves out,” he said. “Our church in the past has been in the majority on these decisions, and today we're in the minority. It would take a lot of energy to leave, and that doesn't help our witness.”

Presbyterians had been debating restrictions on the ordination or marriage of gays and lesbians since the 1970s.

But the tipping point came four years ago when presbyteries ratified the ordination of gays and lesbians as pastors, elders or deacons by a 56-44 percent margin.

This year so far, the rate of ratification is even higher. Nine presbyteries that voted against gay ordination in 2010-11 now support gay marriage, compared with two that switched in the other direction.

The ratification votes are conducted by ordained pastors and elders at presbytery meetings.

The Huntingdon Presbytery in Central Pennsylvania voted narrowly in favor of redefining marriage — reversing its disapproval of gay ordination by a similarly close vote four years ago.

Its general presbyter, the Rev. K. Joy Kaufmann, said people debated respectfully at the presbytery meeting and drew on biblical, sociological and personal arguments.

“Ours is a small and highly relational presbytery,” she said. “I cannot say we're doing anything magical that makes it a more civil place except we know each other, so everyone matters.”

The changes come in dramatic cultural shifts, such as the rapidly expanding legalization of gay marriage and the growing acceptance of gays in other liberal churches and social organizations.