The group, including businessman Wheelock Whitney, says it is united in defeating the proposed amendment.
The growing fight in Minnesota over a constitutional amendment to define marriage is opening some fissures within the Republican Party, which supports the move to ban same-sex marriage.
On Thursday, an unusual alliance of Republicans joined forces to declare their opposition to the amendment that will go before Minnesota voters on the 2012 ballot.
"There's nothing, absolutely nothing in my Republican value system that supports marriage bans," said Wheelock Whitney, a longtime GOP donor and adviser. Whitney, an 85-year-old businessman, was joined by GOP state Rep. John Kriesel, a war veteran who said it makes no sense to "fight against people's happiness." Alongside Kriesel was Susan Kimberly, a transgender former St. Paul deputy mayor under Republican Norm Coleman, and other Republicans who said they are united in defeating the marriage amendment.
Many Republican officials say the definition of marriage should go before voters and that the amendment should pass. In its party platform the state GOP says marriage should be defined constitutionally as the union of one man and one woman and all but a handful of Republicans supported the amendment in the Legislature.
It is the platform that reflects the party's values, GOP state party Chairman Tony Sutton said, not the new Republican coalition opposing the amendment.
"The party recognizes that not all Republicans might agree with all of the party platform at all times," Sutton said. "Debate is healthy, but at the end of the day the [Minnesota Republican Party] stands behind and supports its activist[s] and passage of the marriage amendment."
So far, no state has yet voted down such a ballot amendment.
Chuck Darrell, spokesman for the pro-amendment Minnesota for Marriage, said Minnesota will not be the first.
"The marriage amendment will attract a large percentage of Democratic votes and hold almost all GOP votes," he predicted. Darrell pointed to exit polls from California that showed more than 80 percent of Republicans, 70 percent of blacks and 56 percent of union members supported that state's marriage question in 2008.
But other Republicans say the ground will be shakier in Minnesota. "My instinct tells me this is the wrong place for traditional marriage folks to have a referendum on this issue," Republican political operative Vin Weber said recently. Weber, a former Minnesota congressman who now is a national power player, said backers took "a huge gamble in putting that on the ballot."
Some Republicans say their opposition is rooted less in notions of marriage equality than in holding true to their principles about limited government and liberty.
State Rep. Tim Kelley, R-Red Wing, said he opposes it because it is the conservative thing to do.
"From my standpoint, as Republicans we espouse a lot of less government, less government, less government," said Kelly, an assistant majority leader. The marriage amendment is about more government intrusion, he said.
Kelly voted against bringing the ballot question before the Legislature but did not join his colleague Kriesel in the announcement of Republicans Against the Marriage Amendment on Thursday. While his position has not changed, he said he is still sorting through whether the anti-amendment campaign fits within his values.
He said he received little flak from constituents on his vote against the ballot question. Most younger voters simply do not care about defining marriage. Economic issues, not social ones, are a bigger concern these days, he said.
But, he said, voting against most of his colleagues "was awkward because you are viewed as going against your party."
Rachel E. Stassen-Berger • Twitter: @rachelsb