The two sides battling over a proposed constitutional amendment banning same-sex marriage in Minnesota have raised more than $1 million apiece but in dramatically different ways that highlight a new and untested twist in state campaign finance law.

Amendment opponents count thousands of individual donors, including a number of prominent Minnesota business leaders with deep pockets, according to the most recent campaign finance reports.

Those reports also show that amendment supporters raised $1.2 million, mostly from three heavyweights: the Minnesota Catholic Conference, the Minnesota Family Council and the Washington-based National Organization for Marriage. A relatively new state law allows groups giving to ballot organizations to protect the names of contributors.

Jason Adkins, executive director of the Catholic Conference, which gave $350,000 to Minnesota for Marriage, said his group has complied with the law.

"My question is for the other side: What do they seek to find by disclosing more than what we have already disclosed?" Adkins said. "What's the aim? What is it that they want to know?"

Sen. Scott Dibble, DFL-Minneapolis, said greater disclosure could be revealing. "They are trying to find an excuse to hide large sums of cash," said Dibble, a board member of Minnesotans United for All Families, the largest opposition group.

Mike Dean, executive director of Common Cause Minnesota, a government watchdog group, said his group will file a complaint to the state Campaign Finance and Public Disclosure Board within days challenging the campaign finance reports of pro-amendment groups.

"They've been testing where there are holes in the dike over the last several months," Dean said. "They basically exploited the holes."

The campaign finance report of Minnesota for Marriage, outside of the big three groups it tapped, listed only seven individual donors on its report, who gave a total of $2,100.

Amendment proponents say that the reports document just the first wave and that they too will have a grass-roots network of individual contributors that rivals the 5,000-plus donors on the other side.

Minnesota for Marriage said the three groups are crucial to its fundraising efforts because of the harassment and intimidation that sometimes follow marriage amendment supporters and those who contributed to similar campaigns in other states.

Rep. Steve Gottwalt, a St. Cloud Republican who sponsored the amendment, was shouted at as state troopers ushered him and his wife out of the State Capitol after last year's floor vote. Target Corp. endured a stinging backlash two years ago after it donated to a group supporting former GOP gubernatorial candidate Tom Emmer, who supported the marriage amendment.

Marriage amendment opponents say supporters' objections are a bogus argument designed to disguise the fact that their national effort is driven largely by a few wealthy contributors.

Dibble said amendment supporters have no proof or examples of contributors being harassed in Minnesota. He noted that gays and lesbians have been bullied and harassed for decades, yet thousands of Minnesotans have given money knowing their names would be public.

Investigation sought

The national Human Rights Campaign has asked state campaign officials to investigate who is funding the National Organization for Marriage, which raised $284,000 to push voters to adopt the amendment.

The head of the Campaign Finance and Public Disclosure Board is not surprised that groups are lining up to complain. The board has faced criticism from all sides since a 2010 law change that some say doesn't require enough disclosure and others argue requires too much information.

"This is a very charged question on the ballot," said Gary Goldsmith, the board's executive director. "Both sides are passionate about this issue."

Under the law, contributors who give more than $100 to an outside group directly targeting a ballot question must be disclosed. But if contributors give blindly to an umbrella organization without knowing the money will be redirected to a ballot question campaign, the organization has more latitude to withhold donor names.

brad.schrade@startribune.com • 612-673-4777 baird.helgeson@startribune.com • 651-222-1288