Only in the heat of an election season would TV mobster Tony Soprano and President Bush have something in common.

They're both stars in a wave of political ads aired in Minnesota not by candidates or parties, but by independent groups investing millions of dollars to defend their interests in the elections.

Some of these groups want to make it easier for unions to organize. Others want to prevent that. Some want to challenge the pharmaceutical industry. Others are financed by drug industry bigshots.

Still other groups push agendas concerning war and peace and social policy.

In just five weeks on Minnesota television, from early September to early October, a dozen independent advocacy groups spent more than $5 million trying to influence elections. That's roughly what Republican Sen. Norm Coleman and DFLer Al Franken together spent over the same time in the most expensive U.S. Senate race in state history.

Unlike campaign contributions to political candidates, which must be fully disclosed, funding for ads from many outside groups is far less transparent.

And the contributors to the latest generation of advocacy groups can sometimes be nearly impossible to trace.

"It's hard for anybody to get an idea what's going on," said Craig Holman, campaign finance lobbyist for Public Citizen, a nonpartisan watchdog group in Washington that has worked hard to uncover donors.

In a campaign season awash in tough political commercials, advocacy group ads are among the edgiest, freeing candidates to spend more time projecting positive images in the final days before the election.

Even as Coleman recently decried negative advertising, the pro-business Americans for Job Security ran ads in his behalf accusing Franken of planning the "biggest tax increase in history."

At about the time that DFLer Elwyn Tinklenberg rolled out a feel-good biographical ad in the Sixth Congressional District race, the pro-union Alliance for a Better Minnesota showed his Republican opponent, Rep. Michele Bachmann, "kissing up" to an unpopular President Bush.

Narrower focus: Union issue

While the ads of candidates typically focus on issues that resonate with large audiences, outside groups sometimes push more obscure issues to defeat candidates antagonistic to their financial interests. A large chunk of the money spent by groups in Minnesota has centered on an arcane union issue that may have baffled many viewers.

The Coalition for a Democratic Workplace bought prime-time ads likening union bosses to mobsters from the "Sopranos" TV show and linking them to Franken and his support for a union-supported bill in Congress. The coalition counts the U.S. Chamber of Commerce and many other business groups as members.

The bill the coalition opposes would make it easier for unions to organize by giving them the option of gathering signatures on cards from a majority of workers rather than holding a secret ballot election. Business groups say it would allow labor leaders to coerce workers by forcing them publicly to decide whether to sign.

"My pal Al," remarks one of the union bosses in the coalition ad.

The bill wouldn't abolish secret ballots but would give workers seeking to organize the chance to choose between an election, should 30 percent of all workers request one, or the so-called card-check process, which automatically certifies a union if a majority of employees sign up. Unions say the option is needed because businesses sometimes intimidate organizers before a federally approved election can be held.

Just how much the coalition spent on the ads is unclear. Unlike some other groups seeking to influence an election, the coalition didn't file an "electioneering" disclosure with the Federal Election Commission (FEC) on its spending.

Its spokeswoman Rhonda Bentz said the group didn't need to file because it wasn't electioneering but practicing "public education." She said the spending in Minnesota was "deep into the six, close to seven figures."

The Chamber of Commerce, a coalition member, filed FEC reports disclosing $1.9 million it spent on ads over four weeks in the U.S. Senate race in Minnesota, many of which also attacked Franken on the union issue.

On the other side, the pro-union American Rights at Work ran an ad that used workers on a see-saw as a visual metaphor for the group's argument that the bill was needed for unions to counter business powers. Its FEC disclosures show it spent $516,000.

The Alliance for a Better Minnesota spent $882,000 in Minnesota on ads critical of Coleman on oil policy as well as the one on Bachmann and another opposing Republican Erik Paulsen in the Third Congressional District. Health Care for America Now, which calls for more regulation of health insurance, spent more than $517,000 opposing Paulsen.

Organized as nonprofits

Many of the advocacy groups are organized as nonprofits under the tax code and are not required to divulge much information about their finances.

"I think across the board people want to be able to participate in things ... contribute to these efforts that are legitimate public policy debates ... and they want to be able to do it privately," said Bentz of the business group. "We don't disclose our donors."

But David Schultz, a political science professor at Hamline University who teaches elections law, said the public has a stake in more openness.

"We should have more information about who's funding those groups so we can make judgments on who's behind those ads," Schultz said. The nonprofit strategy amounts to "almost anonymous donations."

The current emphasis on using nonprofits for advocacy comes after groups organized under Section 527 of the IRS tax code came under greater scrutiny by the FEC. The so-called 527 groups must disclose more details about their donors.

Holman of Public Citizen believes that the agency's scrutiny of spending violations by groups organized under section 527 prompted some to funnel their spending through nonprofit entities that draw less attention.

"There may be a lot more spending, but we're not going to know about it," he said.

Pat Doyle • 651-222-1210