MADISON, WIS.-- With the fight over collective bargaining stretching into its third week here, the colorful ground war waged by protesters at Wisconsin's State Capitol continues to take center stage.

But it's the air war -- the barrage of TV ads for and against Gov. Scott Walker's union-busting bill -- that tells the real story about the Badger State battle and the implications for those elsewhere watching it unfold.

Walker, who is just months into his first term, has proposed broad collective bargaining restrictions on most public employees, as well as reasonable benefit cuts.

Stung by his surprise attack and by his refusal to compromise even after unions agreed to concessions, the Wisconsin State AFL-CIO is striking back with ads imploring the state to support public workers' bargaining rights.

An equally unavoidable ad from the Wisconsin Club for Growth urges families to support Walker and protect the state against "special interest" protesters. Never mind that the Club for Growth nationally is an ultra-rich special interest itself.

Also weighing in on Walker's behalf: Americans for Prosperity, a group with strong ties to billionaire oilman David Koch.

Koch was the Libertarian Party's 1980 vice presidential candidate; his platform called for abolishing Social Security, the minimum wage and almost all federal agencies while legalizing recreational drugs, suicide and prostitution.

What appears at first glance to be nothing more than a Midwestern state budget battle is in reality something far bigger.

This is a death match between American's special-interest titans -- wealthy, antiunion corporate-interest groups vs. public-sector unions -- and the clash will shape elections nationally in 2012 and beyond.

Right now, the Club for Growth and its allies have the upper hand in Wisconsin, given the state's GOP-controlled legislature and Walker's giddiness last week when a prankster claiming to be Koch called his office.

While Republicans have the votes to pass the bill, they may be setting themselves and party members across the nation up for the same kind of "shellacking" that President Obama and the Democrats got in the 2010 midterms.

Polls in Wisconsin and elsewhere show that the public approves of benefit cuts for government workers but also strongly supports their right to collectively bargain. (Disclosure: I'm a newspaper union member.)

The Tea Party and the GOP benefited from the perception that Obama and his party overreached on health care, but that doesn't mean they are immune from blowback themselves. Taking away workers' rights sure looks like this movement's overreach moment.

Images broadcast around the world from the Capitol only underscore that. Walker has derided the protesters as out-of-state special-interest groups.

That's wishful thinking. Wisconsin Badger hats and sweatshirts celebrating the Green Bay Packers' Super Bowl win are common.

Protesters camped out at the Capitol include Christa Bruhn, a Madison mom, and her 9-year-old daughter Sham, who brought her pink sleeping bag Wednesday night and had a slumber party with school friends on the third floor.

One floor below, a "knit-in" gave the protest a down-home flavor. Nicole Craig, who works at a Madison nonprofit, proudly modeled a green scarf she'd just finished.

"This is not an angry protest. I think it is injustice that is drawing people here," she said.

Walker and other hard-liners against collective bargaining need a history lesson about how far they've strayed from party roots: Republicans in Minnesota and other states often supported legislation allowing public workers to unionize decades ago.

Nonetheless, the Wisconsin governor chose to start a fight with a formidable foe.

The American Federation of State, County and Municipal Employees (AFSCME) ranks third on the Center for Responsive Politics' "Heavy Hitters" list of political donors.

Between 1989 and 2010, AFSCME spent $43.5 million on federal-level politics -- 98 percent of which went to Democrats.

Also making the Center's Top 10: the National Education Association, the International Brotherhood of Electrical Workers, the Teamsters Union and the Laborers Union.

Virtually all of these organizations had signs or contingents at the Wisconsin Capitol this week. Rarely has such a broad array of labor unions been ready to rumble in Wisconsin and everywhere else.

"You remember how you felt on 9/11? That patriotism that rose up? It's that kind of feeling," said Sandra Burdue, a California nurse and union member who flew in to support protesters. "It's about our way of life, our values and our future."

Joe Heim, a political science professor at the University of Wisconsin-La Crosse, put it this way: "A sleeping giant has been awakened."

The protesters and union representatives use a lot of over-the-top rhetoric. But anti-collective-bargaining bills in Wisconsin, Ohio and others states really are an existential threat to many government workers' unions.

The Wisconsin bill wouldn't completely strip most public workers of collective bargaining (police and firefighters are exempted) but would limit the process to wages; increases beyond certain levels would require a public referendum.

It also would make it significantly harder for unions to collect dues -- a potentially lethal blow.

If this were really about Wisconsin's budget, Walker would have targeted all public unions and not exempted those that often have generous benefits. He would have accepted the concessions and moved on.

The unions had a sweet deal on health and pension benefits. It needed to end.

Walker is betting he'll make a career out of being the governor who broke public unions' back. Maybe so. But the prank call last week will also dog him.

He wasn't talking to protesters, and Democratic legislative leaders claimed he was hard to reach. Yet he quickly made time to take a phone call from fat cat Koch.

That ought to raise questions for years to come about who he's really listening to.

Jill Burcum is a Star Tribune editorial board member and editorial writer.