David Taintor February 15, 2012, 6:15 AM

Washington state has legalized gay marriage, New Jersey might not be far behind, but just over the horizon a bruising battle over marriage equality is looming in Minnesota, where special interest groups are preparing to spend big to affect the outcome.

In November, Minnesota voters will head to the polls to vote on a constitutional amendment that would ban same-sex marriage. Already, the two key advocacy groups facing off over the measure have raised big bucks. Minnesotans United for All Families — a group opposing the amendment — raised $1.2 million in 2011 and boasts a “broad coalition” of people supporting their efforts. Among the group’s 5,000 donors last year, contributions ranged from $1 to more than $40,000.

“This is an extreme measure to change our constitution, to limit a loving couple from ever having the opportunity to be married,” Gia Vitali, deputy campaign manager for Minnesotans United for All Families, told TPM.

The group supporting the constitutional amendment, Minnesota for Marriage, raised about $800,000 last year — no small sum, either. National Organization for Marriage President Brian Brown told TPM that NOM has contributed about $250,000 to the Minnesota for Marriage effort. “We’re confident that the people of Minnesota are going to amend their constitution to protect marriage,” Brown said. Minnesota for Marriage did not return TPM’s requests for comment.

Brown, of the National Organization for Marriage, said he expects the money to keep flowing into Minnesota in the months to come. “We’re going to continue to support the effort in Minnesota.”

David Schultz, a law professor at Hamline University in St. Paul, estimates that $8 million to $10 million will be spent on advertising on the issue. “If I’m working for a television station, I’m thrilled to death,” he told TPM.

Polls show that it could be a close fight. A Public Policy Polling (D) survey from late January showed 48 percent of voters approve the amendment and 44 percent are opposed. Older voters tend to support the amendment, while voters under 65 years old oppose it. A local SurveyUSA/5 EYEWITNESS News poll showed 47 percent of the 542 respondents would support the amendment. Thirty-nine percent of respondents would oppose it.

Vitali said she hopes to tip the conversation in her side’s favor by having gay and lesbian couples explain to Minnesotans why marriage is so important to them. Hearing that testimony — that gay and lesbian couples want to announce their love in front of their friends and family and get married like anyone else — has a profound impact, Vitali told TPM. Those conversations will happen over the airwaves and in more traditional venues, she said.

Elected officials at the city level have weighed in on the issue, too. The Minneapolis City Council last week voted unanimously to oppose the ballot amendment. Mayor R.T. Rybak — who also serves as vice chairman of the DNC — said in a statement that “We took this step because it is critical that every person in Minneapolis can make a commitment to the person they love.” The city councils of St. Paul — the state’s capital — and Duluth, a northern city on Lake Superior, also oppose the amendment.

Professor Schultz expects the amendment to fail — in part because of a peculiarity in Minnesota state law. To amend the state’s constitution, a majority of all voters who show up to the polls in November would have to approve the amendment. If 1 million people vote in November, for example, 500,001 people would have to approve the amendment for it to pass. And if a person shows up to vote in the general election, but avoids voting on the amendment, it effectively constitutes a “no” vote, Schultz said.

“That peculiarity in the amending process makes it difficult to pass an amendment,” he said.

Gay Marriage, Minnesota