The Rev. Walter Waldron's homily usually earns a smattering of amens, but his latest talk from the pulpit at St. Patrick Church got him a round of applause. Waldron rallied support Sunday for a petition that calls for banning gay marriage in Massachusetts.

At the end of Mass, he held up a copy of the petition and urged parishioners to sign it in a room at the rear of the church.

"It just seems so strange for me to stand here today and preach what I think is so obvious: Marriage is between a man and a woman," Waldron said. "It's not just our faith. It's for the good of society."

Over the weekend, supporters of the proposed constitutional ban on same-sex marriage (search) launched a signature drive at churches across the state. They must collect more than 65,000 signatures before Nov. 23 for the question to qualify for the 2008 ballot, but its sponsors hope to gather double that number to protect against a challenge.

Supporters of gay marriage, led by the MassEquality (search) advocacy group, gathered outside many churches Sunday to protest the signature drive.

"We completely respect people's right to worship," said Marc Solomon, the group's political director. "However, we are very concerned that the church hierarchy has made taking away marriage equality — and replacing it with nothing else — such a high priority."

Boston Catholic Archbishop Sean O'Malley (search) has urged parishioners to sign the petition. Some Protestant churches in this heavily Catholic state also planned to collect signatures.

Former Boston Mayor Raymond Flynn (search), one of the petition's chief sponsors, said church officials have an obligation to "speak out on important issues in the civic arena."

"The marriage petition is not against gays but for children," he said. "We believe that a loving family with a mother and a father is the best environment for children to be brought up in."

Last month, the state Legislature defeated a proposed constitutional amendment that would have banned gay marriage but created civil unions for same-sex couples. The proposed ballot question is more restrictive, banning gay marriage without creating civil unions.

Massachusetts is the only state that allows gay couples to wed. Vermont and Connecticut recognize civil unions.

At St. Thomas Aquinas Church in Boston's Jamaica Plain (search) neighborhood, MassEquality supporters approached parishioners and urged them not to sign the petition.

"I want them to see the face of someone who is married so they can see how benign and human we are," said Elizabeth Anker, 51, who married Aina Allen, her partner of 20 years, last year. "They don't have to blindly sign a petition because the hierarchy of the church told them to."

At St. Patrick, in Boston's Roxbury neighborhood, more than half of the roughly 50 people who attended Waldron's Mass signed the petition. Earlier, at least 30 parishioners signed the petition following a Mass said in Cape Verdean.

"I don't believe two men or two women should marry. That's not what God intended," said Connie Fidalgo, who collected signatures at a table outside the church.

Waldron said he isn't worried that his outspoken support for the petition would offend some members of his church.

"We're not crossing the line between church and state," he said. "This is not only a societal issue. It's a moral issue."