Why are union contracts the third rail?

The WSJ penned an interesting editorial yesterday on Secretary Duncan and Michelle Rhee, noting that, while the secretary supports important reforms, he hasn’t helped the chancellor in her donnybrook with the union. (I recently wrestled with the secretary’s apparent willingness to address reform at the policy level but unwillingness to take on collective bargaining agreements.) This quote from the WSJ editorial jumped out at me....Read it here.