Marylanders, who have been inundated by casino ads for the past month, are about to see a campaign blossom into full view over another high-profile ballot measure: same-sex marriage.

With barely five weeks until Election Day, groups on both sides of the debate are poised to make their cases in a blitz of television ads, mailers and other appeals that will alternately try to put a human face on the relationships of gay couples and warn of the consequences of allowing them to wed.

Until now, opponents have mounted a relatively quiet campaign, mobilizing through the state’s churches and civic organizations. That included an event last week featuring the archbishop of Baltimore and plans this Sunday for clergy in churches across the state to preach against changing the definition of marriage.

Proponents of Question 6 have been most visible raising money for the fight, gathering everywhere from the homes of local supporters to a New York rooftop bar where guests mingled with an array of celebrities, including Susan Sarandon. Last week, “American Idol” runner-up Adam Lambert spoke out for equal rights between songs at a benefit concert in the District.

At stake is not only a major policy for Maryland, but also history. Liberal-leaning Maryland is among three states where voters could affirm same-sex marriage at the ballot box in November — something that’s never happened before.

How states recognize same-sex marriage. (The Washington Post/Source: ACLU)

“Who wants to be the first in that regard?” asked Derek McCoy, a gregarious minister who is chairman of the No on 6 campaign. “We tell people straight up: This is a unique time in history. They have to make sure their voice is heard. It’s not about what any two people want. It’s about our society and future generations.”

Gay nuptials are legal in six other states and the District. But in each of those cases, the law was changed either by the legislature or through court action, not directly by the people.

Maryland Gov. Martin O’Malley (D) signed a same-sex marriage bill into law in March, but it was promptly petitioned to the ballot by a group led by McCoy, giving voters the final say.

Besides Maryland, Maine and Washington have measures on the ballot in November that would allow same-sex marriages. In another, Minnesota, voters will be asked whether to write a ban into the state constitution.

Josh Levin, campaign manager for Marylanders for Marriage Equality, said his group is certainly aware of the historical significance of this year’s battle.

“Just about everybody in Maryland knows somebody who’s gay or lesbian,” Levin said. “They’re our neighbors, our family, our friends and our co-workers, and Question 6 is about treating them fairly and protecting religious freedom at the same time.”

Under the pending law, which would take effect Jan. 1 if voters approve, no religious group would be forced to perform same-sex weddings.

Recent public polling has shown proponents with an advantage of 10 or fewer percentage points. McCoy said he remains undaunted, given that in other states his side has generally performed better at the ballot box than in polling on same-sex marriage measures.

McCoy said his group made a strategic decision not to seek much publicity in recent months, in part because of a decision by the Washington Blade, a publication that caters to a gay audience, to publish the names of more than 100,000 people who signed the petition to put the same-sex marriage law on hold.

“We don’t need to bring any more attention to the people who are with us,” he said.

Instead, his group has worked through “natural outlets” that include churches, he said.

McCoy estimated that 1,000 churches could participate in this Sunday’s coordinated effort to preach against allowing same-sex marriages. Sample sermons have been produced.

McCoy would not discuss the specifics of television ads that are expected to start running early next month but said that “everything we’re going to talk about in those ads is going to be factual.” A national organization is expected to help fund the ads.

The campaign is working with Frank Schubert, a consultant who worked on the successful effort in California to pass Proposition 8, the ballot measure that banned same-sex marriages, and who has been on the winning side of a string of similar contests since then in other states.

This month, Marylanders for Marriage Equality sent a memo to reporters noting the Schubert connection and calling attention to ads in other states that have linked same-same marriage policy to the school curriculum.

“In Maryland, a school’s specific curriculum is decided by local districts,” the memo said. “Teachers and parents decide what is taught in the classroom, and no state law — including the marriage question on the November ballot — changes that.”

McCoy said he considers curriculum issues fair game for upcoming ads, arguing that “teachers are going to teach what’s the law.”

Proponents of same-sex marriage have also produced several dozen clergy members in recent weeks to counter the notion that all religious leaders oppose the right of gay couples to get married.

This month, the Rev. Al Sharpton and about a dozen black pastors from Maryland and well beyond held a news conference at the National Press Club to make known their support for Maryland’s same-sex marriage law.

Proponents have also invested a great deal of time in raising money to pay for the ad war in the closing weeks of the campaign. Reports on how much each side has raised will not be available until next month.

Early next month, Baltimore Ravens linebacker Brendon Ayanbadejo is scheduled to appear at a Monday Night Football watch party with O’Malley. Ayanbadejo’s support for the cause got national attention after Maryland Del. Emmett C. Burns Jr. (D-Baltimore County) unsuccessfully asked the Ravens to silence him.

Last week, Lambert, the glam rocker who rose to prominence on “American Idol,” was the main draw at a benefit concert at the 9:30 Club in the District attended by a diverse audience, including teenagers accompanied by their parents and senior citizens.

“The thing I like about Question 6 is it’s really not about politics at all,” Lambert told the crowd as he took a breather between songs. “It’s a human-rights issue. . . . Everybody has the right to just love who they love.”