“We are worried, but we are ready to fight,” says Barbara Madeloni, president of the Massachusetts Teachers Association (MTA). “We are more ready than ever, actually.”

With 110,000 members, the MTA is the largest union in the state, a status that could soon change once the Supreme Court hands down its anticipated ruling against unions in Janus v. AFSCME [the American Federation of State, County, and Municipal Employees]. That decision would allow public-sector workers — some of whom are currently mandated to pay “fair share” fees if they opt out of full-fledged union membership — to receive union representation and benefits without paying anything. This would expand right-to-work conditions to the entire public sector in the United States, a crisis even for a movement that is accustomed to crises. Say the word “Janus” to union organizers and they say things like “devastating,” “catastrophic,” “cataclysmic,” and “fucked.” And “organize.”

Two years ago, unions escaped with a victory in a similar case, Friederichs v. California Teachers Association, only because the timely death of Justice Antonin Scalia resulted in a 4-4 decision. But no one is counting on a favorable court ruling this time around; hence, a call to arms.