The Midwest is ground zero for organized labor this fall.

In the wake of the failed Wisconsin recall attempt, unions are forging ahead with their 2012 battle plan, pouring cash and resources into Michigan, Wisconsin, Iowa, Indiana, Minnesota and Ohio in an effort to recapture ground lost when Republicans made sweeping gains in the 2010 midterm elections.

At stake is control of state legislatures, a governor’s mansion and potentially the White House.

“Unions will be very active in the Midwest, since that’s where there have been all these state battles for the last year,” said AFL-CIO Political Director Michael Podhorzer. The region has always been a focal point because of the high concentration of union membership, he said, but “the difference that the 2010 elections made is that there will be an additional focus on holding state legislators accountable for how they voted these last two years.”

On defense after a failure to oust Gov. Scott Walker in Wisconsin, labor is intent on halting any further inroads by pro-business forces in other states, trying to preserve its majority in the Wisconsin state Senate and enshrine collective bargaining in the Michigan state constitution.

But labor’s foes say it’s a fool’s errand. Rob Engstrom, national political director for the U.S. Chamber of Commerce, noted the high percentage of union members who voted for Walker last Tuesday.

“The Midwest is always the key battleground, and it always serves as the area where there’s a proxy fight between the business community and labor,” said Engstrom. “If these races are determined on the merits and the substance, then the business community will prevail in 2012 the same way we did in 2010.”

“Wisconsin was Act 1, and we will continue to be engaged as we move forward until November,” he added.

“We’ve seen already that Midwesterners have decided that Big Labor is no longer serving their interests,” said Greg Mourad, vice president of the National Right to Work Committee. “Wisconsin ought to be a warning sign to them that the American public is frankly fed up with government sector unions having such an inordinate amount of power over the public purse.”

Labor’s efforts on the ground in the critical swing states aim to buoy President Barack Obama and other down-ballot Democrats. But big losses could open the floodgates to Wisconsin-style union reforms in other states and further undercut Big Labor’s power in a region it has long dominated. It could also impair Obama’s reelection chances and boost presumptive GOP nominee Mitt Romney’s prospects.

“This is a place that is a bellwether for all of our country,” said Seth Rosen, vice president of the Communication Workers of America’s District 4, which represents workers in Illinois, Indiana, Ohio, Michigan and Wisconsin. “Other places are red states or blue states. These are purple states.”

Here’s a look at the state of play in the region’s hottest combat zones:

Michigan:

The Great Lakes state could offer the labor movement’s best opportunity to score an offensive win on collective bargaining rights this year.

Michigan union advocates are likely to secure a spot on the November ballot for a constitutional amendment that would block or undo state laws to limit unions’ collective bargaining authority. Backers of the initiative submitted nearly 685,000 signatures in support of the amendment Wednesday; they need about 330,000 valid signatures to get the measure on the ballot.

The initiative is aimed at hamstringing efforts by GOP Gov. Rick Snyder and other state Republicans. Snyder hasn’t been a lightning rod for unions in the same way that Walker was in Wisconsin, but he signed several smaller pieces of legislation that irked them.

“It was just a thousand paper cuts instead of the big blow,” said David Hecker, President of the Michigan chapter of American Federation of Teachers.

Unions are also hoping to help push control of the state House to Democrats this fall, further bolstering their defenses in Michigan. GOP representatives outnumber Democrats by 16 in the lower chamber, which flipped to GOP control in 2010. Under the new district lines drawn by Republicans, Democrats face an uphill climb, but national labor leaders are hopeful that the chamber presents a pickup opportunity.

“If I didn’t see any potential, we wouldn’t invest,” said Ricky Feller, associate political director of the American Federation of State, County and Municipal Employees. “You see that there’s a path in Michigan.”