"We're a people of many different faiths, and it's so important that we protect rights equally under the law," he said.
Among several openly gay legislators who helped advance the bill was Delegate Heather Mizeur, who married her lesbian partner during a brief window when same-sex marriage was legal in California in 2008.
Mizeur says she's a dedicated Catholic, despite her opposition to church teaching on marriage.
"The No. 1 tenet of our faith is the primacy of our conscience," Mizeur said. "That was important to me as a young person, sitting there trying to pray the gay away."
Another churchgoing Catholic active in the gay-marriage campaign is 83-year-old Erma Durkin of Glen Arm, whose gay son married his longtime partner in New York last year. Durkin said she's made clear to her pastor that she objects to materials inserted in the church bulletin conveying the Catholic hierarchy's opposition to same-sex marriage.
"You can't command that someone stay celibate and single all their life," Durkin said. "If we find someone we love that much that we want to marry, that's a wonderful thing."
On the other side, Archbishop Lori recently hosted a meeting of same-sex marriage opponents to mobilize for the campaign's home stretch.
"The union of man and woman is not only a good for the couple, but for the entire community of believers and for humanity," Lori told the gathering.
Within the opponents' coalition, the Maryland Marriage Alliance, black pastors are playing a key role. One of them, the Rev. Derek McCoy, is the campaign chairman; he is keenly aware of the high stakes.
"Eyes are on us from around the country," he said. "We have a gargantuan task ahead of us."
Blacks comprise about 25 percent of Maryland's electorate, and polls showed a significant increase in their support of same-sex marriage after it was endorsed in May by Obama and the Baltimore-based National Association for the Advancement of Colored People.
"The question isn't if marriage equality will prevail — the only question is when," said Ben Jealous, the NAACP's president. "The rising generation of young voters is the most diverse and inclusive we've seen. It's only a matter of time until the laws catch up with them."
McCoy believes most Maryland blacks still oppose same-sex marriage and said one of his coalition's challenges is persuading them to vote "No" in the referendum even if they support Obama.
"Some people are in a quandary," he said, "We're telling them, 'Don't vote against your conscience.'"
The Rev. Delmon Coates, pastor of a large, predominantly black Baptist church in Prince George's County, has taken up the banner on the other side. He recently brought national civil rights leaders, including the Rev. Al Sharpton, to the region to endorse same-sex marriage.
As in Maryland, the campaign in Washington state involves a measure signed into law by a Catholic governor, Christine Gregoire, and now being challenged by gay-marriage foes.
The coalition supporting gay marriage has raised more than $8.9 million, compared to about $1.7 million for the opponents. The biggest single donation in support of the law came from Amazon.com CEO Jeff Bezos and his wife, MacKenzie, who donated $2.5 million in July.
Maine's ballot measure marks the first time that gay-rights supporters — rather than opponents — have chosen to put same-sex marriage before voters. A gay-marriage law passed by the legislature in 2009 was quashed that fall after opponents gathered enough signatures for a referendum; this year, gay-marriage supporters used the same tactic to give voters a chance to reconsider.
The political action committee backing same-sex marriage in Maine raised about $3.4 million through September, compared to $430,000 for the leading opposition PAC.
At stake in Minnesota is a proposed amendment that would strengthen the existing law against same-sex marriage by inserting it in the state constitution. If the amendment is defeated, it would still take a legislative act, court ruling or future popular vote to legalize gay marriage.