The group We Are Ohio delivered more than 1.3 million signatures to Secretary of State Jon Husted, though the opponents needed roughly 231,000 valid signatures to get the question on the ballot.

The measure was approved by the Republican-controlled state Legislature in March amid shouts and jeers from protesters in each chamber. But the overall response by protesters in the Rust Belt state, despite its long union tradition among steel and auto workers, paled in comparison to Wisconsin, where protests topped more than 70,000 people. Ohio's largest Statehouse demonstrations on the measure drew about 8,500 people.

That difference has been attributed to Madison's labor legacy and the proximity of the populous University of Wisconsin campus to the state capital.

The fallout from each state's bitter fights over collective bargaining restrictions have also differed.

Unlike in Wisconsin, Ohio voters cannot recall state lawmakers. Instead, opponents of the Ohio law are pushing for its repeal through a referendum.

Nine state senators — six Republicans and three Democrats — are facing recall elections in Wisconsin, where GOP Gov. Scott Walker's collective bargaining law eventually survived a court challenge and took effect.

The We Are Ohio campaign says 10,000 volunteers and some paid workers circulated petitions to get the referendum before voters. The coalition of labor groups and others contends the law is an unfair attack on workers.

Kasich, a first-term governor, and his GOP colleagues argue the legislation will help city officials, school superintendents and others better control their costs at a time when they, too, are feeling budget woes.

Groups on both sides of the debate have been raising money in anticipation of the tough fight over the Ohio law in November.

Kasich has said he plans to play a visible role in defending the law. So far, he has directed his supporters to a website for Building a Better Ohio, a group that wants to keep the new law in place.