For more than 30 years, one of the most influential charitable and political donors in Minnesota has been a woman passionate about issues but guarded about her privacy.

Alida Messinger, an heir to the fabled Rockefeller fortune, has quietly given at least $10 million to candidates and causes over the past decade. Some recent gifts have been extraordinary: $500,000 to a group that last year backed her former husband, Mark Dayton, for governor. And before that, $1 million to help bankroll the ballot campaign for the Legacy amendment, which raised the state sales tax to create 25 years of new funding for conservation and cultural projects.

Now, Messinger is preparing for a new showdown that will be expensive, contentious and, for the first time, public.

She is vowing to do all she can to help the DFL regain control of the Legislature and get President Obama re-elected. Her millions could also become a force in the fight over the constitutional amendment on the ballot next year to define marriage as a union of man and woman -- not gay couples. Messinger, 62, contends GOP politicians are harming Minnesota. "We are not a quality-of-life state anymore," she said. "Citizens need to get involved and say we don't like what you are doing to our state."

Republican leaders scoff at such rhetoric, saying all Messinger really wants is a clear path to political power.

"She is going to try to decimate Republican legislators so Governor Dayton can have free reign over the state to raise taxes and grow the size of state government,'' said Michael Brodkorb, GOP activist and former deputy state party chairman.

Messinger is a New Yorker by birth -- she is the youngest daughter of philanthropist John D. Rockefeller III -- and a Minnesotan by marriage. Her political giving is guided largely by DFL strategy guru Jeff Blodgett, the founding director of Wellstone Action. Blodgett recently left Wellstone Action to lead another of Messinger's favorite causes, WIN Minnesota. That organization, which helped elect Dayton, is now focused on returning DFLers to power in the Legislature.

In addition to Blodgett, Messinger is close to Ken Martin, the new chairman of the DFL. She also considers one of her dearest friends to be Tina Smith, Dayton's chief of staff.

Mike Erlandson, former DFL Party chairman, said Messinger tends to be very quiet and private, but has become "a significant force" in the politics of Minnesota. "She has chosen, by virtue of her ability to support things, to have a very loud voice," he said.

An alliance questioned

During last year's race for governor, state GOP Chairman Tony Sutton complained Dayton was relying on Messinger to raise money for an advocacy group heavily involved in the campaign and intimated that they were coordinating their message -- something that would have been illegal and that Dayton denied. Sutton called it an "unsavory alliance.''

"Dayton likes to rail against the rich,'' he said, "but it's precisely his rich family members who are funding this unprecedented onslaught of negative personal attacks."

Messinger acknowledges her involvement in the 2010 governor's race was strong. But she insists that she did not work specifically for Dayton over his DFL rivals.

"Nothing could be farther from the truth," she said, noting that she donated to the DFL in June 2010, when the party was still backing its endorsee, former House Speaker Margaret Anderson Kelliher.

"Honestly, most people didn't think Mark could win," Messinger said. "I just wanted the one who could win."

Dayton and Messinger have been divorced since 1986. They remain close, both as parents and through an arm's-length political alliance. They do not, they say, collaborate on policy.

"I think he trusts me and respects me, but I am not part of his inner circle," Messinger said. She is now married to Bill Messinger, president of Aureus, an addiction recovery organization.

Dayton said in a statement that "Alida is the most extraordinary contributor to social causes I have ever known. ... She has given and done so much, in countless, untold ways, to benefit our state."

Republican leaders say Messinger is rushing to Dayton's aid again with her immense wealth.

"Alida Messinger has used her money to bankroll some of the largest buckets of mud that have been thrown in the last election," Brodkorb said. "She's now trying to use her money to get rid of her ex-husband's enemies in the Legislature. She clearly believes Republican legislators are an obstacle to her ex-husband, who is pursuing a liberal agenda they both truly want."

Others have learned not to underestimate Messinger.

Phil Krinkie, president of the Taxpayers League of Minnesota, which fiercely opposed the Legacy amendment that Messinger championed, recalls being "shocked" to see her $1 million donation to that cause at a time when he was pleading for $1,000 contributions.

"I had never seen that before in a local issue," Krinkie said. "I was certainly taken aback by that. We all know money helps drive the message. She obviously has a lot of money and can transfer that into a significant amount of influence."

Angry and ready to spend

Messinger is a descendent of the Standard Oil fortune. Her brother is Democratic Sen. Jay Rockefeller of West Virginia.

"My father raised us all to consider our money a trust to us. It was passed on to us; we didn't earn it," Messinger said. "I felt a tremendous responsibility."

Her first big philanthropic endeavor came in the late 1960s, when she was a college student in California and wanted to block logging companies from clear-cutting redwood forests. More than 40 years later, the anger she felt toward environmental degradation still burns.

"I have the same feeling of indignation at companies and corporations that scoop up natural resources and then dump pollutants," she said.

When she met and married Dayton, she slid into the role of a stay-at-home south Minneapolis mom who, for the next three decades, would also pump millions of dollars into local and national causes, including community development agencies, women's rights and environmental causes.

A political turning point came for Messinger in 2004, with the re-election of President George W. Bush. "I just felt that administration was the opposite of everything I believed in," she said. "It was the first time I felt I had to do more than just write a check. I couldn't sit still after that."

Now, she says, she is angry that many lakes in her chosen state are too polluted for people to eat the fish from them. She is frustrated Minnesota schools no longer lead the nation. All the reasons she loved the state so much when she moved here, she said, are under attack.

"I feel like what we are up against in this country is so serious that it really doesn't matter how I feel" about remaining private, Messinger said.

She said she is proud of the work Dayton is doing as governor, but that "it's a miserable, difficult job to have right now" with Republicans controlling the Legislature.

That's why she's vowing to do all she can to help the DFL win back the Legislature next year. Her husband, Bill, meanwhile, has his own keen interest: Defeat of the constitutional amendment on marriage.

Messinger said she knew when she started getting involved in politics it would end the privacy she so carefully guarded for decades. But she said it infuriates her that a generation of good philanthropic work can be undone in a moment by a bad governor or Legislature. That, she said, is what's driving her now. Friends and confidantes said they expect her upcoming political activity to mirror her philanthropic work -- she comes in big, and then leaves people and organizations she trusts to do the work they promised.

Blodgett, whose political organization benefited from Messinger's donations in past years, said she does not get intimately involved in the details of a campaign.

"She's not a kingmaker,'' he said. "She takes her resources and focuses them on what she really believes."

For her part, Messinger says she has no idea how much she has given to causes over the years -- or how much she will end up contributing in the months ahead.

"And even if I knew,'' she added, "I wouldn't tell you."

Baird Helgeson - 651-222-1288