In 2012, the corporate education-reform group Stand for Children put a question on the Massachusetts ballot that would have destroyed teachers’ seniority and tied evaluations to students’ test scores. And they lined up $10 million to pass it.

Terrified, leaders in the Massachusetts Teachers Association begged the unelected group to negotiate instead of going forward with the referendum. Rather than draw a line in the sand against the attacks on teachers, the MTA leaders were quick to offer concessions to the billionaire-backed group in exchange for taking the question off the ballot.

For an emerging rank-and-file caucus in the MTA, the Educators for a Democratic Union, the leaders’ instinct to negotiate the terms of their defeat rather than fight the deal represented everything that needed to change about the union.