Scores of Maine churches will pass the collection plate for the second time at Sunday services on Father’s Day to start fundraising for the lead opposition group to November’s ballot question proposing to legalize same-sex marriage.

Between 150 and 200 churches are expected to raise money for the Protect Marriage Maine political action committee, said Carroll Conley Jr., executive director of the Christian Civic League of Maine and a member of the PAC. Conley is also trying to drum up support from religious leaders around the country.

It’s unusual, but not unprecedented, for churches to take up collections for political causes. Maine’s Catholic diocese says it raised about $80,000 with a collection in 2009 in its effort to overturn the same-sex marriage law that was passed by the Legislature and later rejected by voters.

The Catholic Church isn’t campaigning this time, instead focusing on teaching parishioners about the sanctity of marriage between a man and a woman.

Father’s Day, June 17, seemed an appropriate time to kick off this year’s fundraising because of the day’s focus on family, Conley said. Additional collection-plate offerings at churches are expected in the months ahead.

“The messaging we’re using is that those who are seeking to redefine marriage in Maine believe there’s no difference between moms and dads,” Conley said. “We believe those differences are relevant. We don’t think the differences in the genders are societally imposed roles, and we believe that children benefit when they’re in that ideal environment where there’s a mom and dad.”

Protect Marriage Maine has been in contact with about 800 churches across the state and expects 150 to 200 to participate in the Father’s Day collections, Conley said. They include Methodist, Baptist, Pentecostal, Nazarene, Church of God, Wesleyan, Evangelical Free, Advent Christian and other denominations.

Others churches of various denominations are working to support the ballot measure.

Some churches have hosted phone banks where congregation members have made calls in favor of same-sex marriage, said the Rev. Sue Gabrielson, minister at the Sanford Unitarian Universalist Church. Other churches have held educational forums and training sessions on door-to-door canvassing.

The referendum, she said, is about inclusion, a “loving God” and being nonjudgmental and compassionate. “What we want is for people to know that this is a religious issue,” she said.

Episcopal Bishop Gene Robinson of New Hampshire, who created an international uproar when he became the first openly gay bishop in the Anglican church in 2003, will come to Maine in early June on behalf of the campaign in support of gay marriage. He will appear at three screenings of the film “Love Free or Die,” which depicts his life, in Portland, Lewiston and Ellsworth.

Supporters of the same-sex marriage proposal have said they expect to raise $5 million or more for their campaign. Opponents have said they expect to raise far less, but collection plate offerings will go a long way toward helping fund the campaign, Conley said.

Conley has been in Washington, D.C., this week at a pastors conference organized by the conservative Family Research Council. There, he met with gay-marriage opponents from Minnesota, Washington and Maryland, where same-sex marriage ballot initiatives are being debated.

Minnesota will decide in November whether a ban on gay marriage should be part of the state Constitution. Maryland and Washington are expected to have ballot measures seeking to overturn same-sex marriage laws that were passed recently by their legislatures.

Conley also has endorsements from well-known gay-marriage opponents who recorded video and audio clips to be played at churches in Maine’s collection-plate drive, he said. Those clips will be sent to the state’s Christian radio stations as public service announcements.

Conley said Friday that he shot video endorsements this week in Washington from Ravi Zacharias, an evangelical scholar; Mark Harris, president of the Baptist State Convention of North Carolina; Harry Jackson, a Maryland pastor and a staunch gay-marriage opponent; and Family Research Council President Tony Perkins.

Conley said he realized that churches should play a central role in the Maine campaign after being in North Carolina this month when voters approved an amendment to the state Constitution affirming that marriage may be only a union of a man and a woman.

“I was impressed with the coordination I saw among the faith community in North Carolina,” he said.