Just off the main drag in Pine City one recent Sunday, the seeds were being sown for what promises to become a grueling, 17-month campaign over Minnesota's gay marriage amendment. Signing up volunteers at one of the country's only rural gay pride festivals, organizer Donald McFarland said he is heeding the advice of predecessors in other states.

"Everyone has said 'start today, start today, start today,'" said McFarland, a veteran Democratic political consultant now running Minnesotans United For All Families, a coalition of groups trying to defeat the amendment that would enshrine only heterosexual marriage in the state constitution.

Amendment supporters haven't moved as quickly or as publicly, but they plan to tap a statewide network that includes 1,600 churches and a mailing list of more than 300,000 social conservatives.

Together, the groups are setting the stage for a national battle over gay marriage in Minnesota in 2012. Warring campaigns backed by heavyweight groups across the country will spend millions to sway voters here, one of the only states expected to vote on the issue next year.

Supporters of the ballot measure to define marriage as solely between one man and one woman have an impeccable track record. Similar constitutional amendments have passed in all 29 states that put the question to the voters.

"We're hopeful that Minnesota will be the first state in which things begin to change," said Sarah Warbelow with the Human Rights Campaign (HRC), the nation's largest gay, lesbian, bisexual and transgender rights group, which has joined the coalition. Warbelow says public opinion has been moving in the HRC's favor since the last wave of such referendums in 2008. A May Star Tribune poll showed 55 percent of Minnesotans oppose the marriage amendment.

"If proponents of same-sex marriage actually believed the polls that they keep trotting out, they should welcome a vote," shot back Brian Brown, president of the National Organization for Marriage, a group based in Washington. Brown registered as a lobbyist in Minnesota last month to push for the amendment.

National Organization for Marriage is part of the coalition supporting the measure, known as Minnesota for Marriage, which includes the Minnesota Family Council and the Minnesota Catholic Conference. While gay marriage is already banned in Minnesota, supporters say passage of the amendment would block legislative efforts to change the law.

For Minnesotans United For All Families, organizing began the moment the amendment passed, using platforms like Facebook.

Activists are gearing up to raise start-up dollars for what Warbelow estimates could be $6 million to $8 million in campaign spending by each side. McFarland's coalition will host two fundraisers in the next two weeks, including one featuring Gov. Mark Dayton on Monday.

Disclosure advice

A hearing on Tuesday could decide how large both campaigns grow. The state's campaign finance board will revisit a 14-year-old advisory opinion that concluded corporations -- businesses and nonprofits alike -- are not required to disclose their own donors when giving to ballot question committees.

"It could be huge," McFarland said of the decision's potential impact.

Brown said National Organization for Marriage, which has brought legal action in other states regarding disclosure laws, opposes changing the opinion and plans to have an attorney present who will likely testify. He added that it is "odd" that there is a "push to change the rules in the middle of the game." Warbelow said HRC will not testify.

The largest dollars will fund massive media campaigns, which aren't likely to take shape until 2012. Until then, both sides say, a central focus will be educating people and urging them to have conversations with friends and family.

Jason Adkins with the Catholic Conference said they are still honing a strategy to relay their message through Catholics. "We ... need to equip them with the arguments that they'll need to take to their families, to have around the water cooler," Adkins said. "This is going to be a very public discussion."

Monica Meyer, executive director of OutFront Minnesota, a leading group in the fight against the proposed amendment, said her group will be signing people up at pride festivals and county fairs this summer while hosting training sessions to guide people on how to talk about the amendment.

[MN]Love, a group that encourages people to write letters to friends and family about the amendment, is also focusing on informal interactions. "There are lots of us that have parents that are on the fence. Or grandparents who are on the fence," said Michael Miller, the group's leader, at a recent fundraiser in St. Paul.

Some groups have sprouted out of a mere idea, such as Minnesota Artists for Equality. Co-founder Adam Whisner, an actor, intends to create a database of artists who can donate their talents to defeat the amendment. If OutFront wants to make a bumper sticker, he said, "They'll have the list of a couple of people who will say, 'Yeah, I'll do that for free, because I believe in this.' "

Debates can turn ugly

Debates over gay marriage have the potential to turn ugly fast. Only three weeks into the campaign, both sides already are accusing their counterparts of taking the low road.

Adkins says it started before the amendment vote took place in the Legislature, when gay marriage supporters showed up en masse at the Capitol. Looking back, he bristles at chants like, "No hate in our state!"

"Part of having a respectful dialogue is recognizing that reasonable people can disagree and they may have good reasons for disagreeing and it's not just because they hate people," Adkins said.

Archbishop John Nienstedt of the Archdiocese of St. Paul and Minneapolis, who argued for the amendment in a DVD sent to Catholics last fall, also pushed back in a column last week. "Regrettably, the media and some secular commentators have chosen to mischaracterize this measure as anti-gay, mean-spirited and prejudicial. This is not the case or the intent behind the initiative," Nienstedt wrote.

Amendment opponents, meanwhile, were outraged to find material on the Minnesota Family Council website asserting that a "disproportionate number" of homosexuals are pedophiles and that some homosexuals ingest urine and feces, and engage in bestiality.

The Family Council soon removed the document from its site. "It does cross the line when that kind of stuff gets introduced into this," said McFarland.

Family Council spokesman Chuck Darrell said "it was taken down because it was a distraction." He would not say whether the council stands behind the document.

Lawmakers who broke with their party on the issue also will be a focal point of the next year's campaigning.

Stonewall DFL, a caucus of the DFL party, is taking the rare step of seeking candidates to run in primaries against the three DFL lawmakers who supported the bill.

"Frankly, to me, what's the difference between having one of them or a Republican sitting in that seat?" said the group's chairman, David DeGrio.

Rep. John Kriesel, meanwhile, is getting a new welcome from gay rights supporters. One of only four Republicans to vote no, Kriesel will speak about the amendment this week at an event hosted by Republicans Against the Minnesota Marriage Amendment.

Eric Roper • 651-222-1210 Twitter: @StribRoper