Elizabeth Fire Department firefighters in Trenton, N.J., protest staff cuts and promote public safety. (AP)

Wisconsin Republican Governor Scott Walker is threatening pink slips to state workers if the legislature doesn't pass his budget repair bill that would curtail union's collective bargaining rights. In Ohio, a bill that would ban union strikes passed the Senate last week, and now goes to the house. In New Jersey, firefighters and police officers protest staff cuts this week.

But amid the struggle over the future of unions, a New York Times/CBS poll found that more than two-thirds of Americans oppose efforts to weaken collective bargaining. And more than half of those surveyed say they are undecided about how they feel about unions, or haven't heard enough. We have a history lesson on unions with Bruce Laurie, professor emeritus of labor history at University of Massachusetts.