As a young labor organizer in Los Angeles, Antonio Villaraigosa worked for the city’s teachers, honing his political skills in the fight for a good contract. The union loved him back, supporting the Democrat’s election to the State Assembly, City Council and, finally, the mayor’s office he occupies today.

But now, Villaraigosa, a rising star in the national Democratic Party, has a different view. He calls the teachers union “the one, unwavering roadblock” to improving public education in Los Angeles.

Villaraigosa is one of several Democratic mayors in cities across the country – Chicago, Cleveland, Newark and Boston, among them – who are challenging teachers unions in ways that seemed inconceivable just a decade ago.