Michigan’s unions are asking voters to approve a referendum on the ballot this November, known as Proposal 2, that would lock a series of labor protections into the state Constitution, including the right of public sector unions to bargain collectively and a prohibition against the legislature’s enacting a “right to work” law. The ballot campaign represents an attempt by unions and their Democratic allies to slow or stop the wave of Republican-backed measures adopted in Wisconsin, Indiana, Ohio, Tennessee and other states in the last two years to curb collective bargaining and weaken unions, especially those representing government workers. “Besides the presidential race, Proposal 2 is probably going to be the most significant thing on the ballot nationally,” said F. Vincent Vernuccio, director of labor policy at the Mackinac Center, a conservative research center based in Midland, Mich. “Michigan is surrounded by Wisconsin, Indiana, Illinois and Ohio — states that have taken wildly different views of private and public sector unions. The nation is on a teeter right now on union matters, and Michigan will give momentum to one side or the other depending on how this plays out.” Business groups and Michigan’s Republican governor, Rick Snyder, say that if the referendum to enshrine labor rights in the Constitution is approved, it will cast a major cloud over the state’s business climate — broadcasting to the world that organized labor, whenever it deems fit, can use its muscle to go to the voters to trump the legislature and governor. “Michigan’s union bosses are field-testing a new weapon,” said Rich Studley, president of the Michigan Chamber of Commerce. “If this weapon is successful in banning legislation, we’ll see it deployed in the 21 other states that allow initiatives and referendums.” Further flexing their muscles, unions are sponsoring two other proposals on the Michigan ballot. One would repeal a law that allows emergency managers appointed to oversee financially distressed communities to void union contracts. Another would amend the Constitution to guarantee home health aides the right to unionize. Both sides are flooding the airwaves with ads about Proposal 2, with each side accusing the other of using misleading scare tactics. In one union-backed commercial, for example, a firefighter is wearing an elaborate fireproof apparatus over his head. “This air pack I’m wearing gives me 30 minutes to look inside your burning house and find you,” he says. “Having the most modern dependable equipment when the clock is ticking, that counts. If it comes from collective bargaining, the politicians can’t cut it without our say-so.” Opponents are broadcasting an ad that begins with a child leaving for school. “When we send them off in the morning, we should be certain they’re safe in school,” the voice-over says. “If Proposal 2 passes, it would eliminate safety rules for school bus drivers. Worse, Proposal 2 could prohibit schools from removing employees with criminal records. That’s dangerous for kids and terrifying for parents.” Although most of the campaign’s financial disclosures are not due until after the election, political experts estimate that more than $30 million will be spent in the fight, with national business and labor groups contributing substantial financing. At the moment, the proposal’s chances of passing are difficult to predict. Proponents had a significant lead at first, but that has eroded as business-backed groups have escalated their attacks. A Detroit News poll released Oct. 12 found that 43.2 percent of the 600 people surveyed supported the proposal, and 41.8 percent opposed it. The difference was within the poll’s margin of error. Union leaders say Proposal 2 has a simple aim: to protect collective bargaining against further assault.