Levin said Snyder "doesn't understand what made Michigan the ideal place" for the middle class.

"Employers say, 'Look, let's have a relationship with workers and have them have a voice in the workplace,' " Levin said. "That's good for everybody. And ask the leaders of the Big Three, do they want unions to be able to be represented, people to be able to be represented, have a voice in the workplace? And they say that's better for economic development in Michigan."

President Obama weighed in against the right-to-work bill during a speech Monday in Michigan.

"I've just got to say this," Obama said at the Daimler Detroit Diesel plant. "What we shouldn't be doing is trying to take away your rights to bargain for better wages and working conditions. We shouldn't be doing that."

Early Tuesday morning Michigan police lined up outside the state capitol in response to planned protest in opposition to the right-to-work law. Local reports expected thousands of protesters to march in opposition to the law.