Joe Biden addressing the National Education Association’s annual meeting in 2012. Photo: Mark Wilson/Getty Images

Joe Biden earned a formidable labor endorsement on Saturday night: America’s largest union, the National Education Association, formally recommended Biden to members as the Democratic Party’s presidential nominee, and pledged to mobilize its 3 million members — most of whom are women — on his behalf.

In a statement calling Biden “a tireless advocate” for public education, NEA president Lily Eskelsen Garcia said the former vice-president “understands that as a nation we have a moral responsibility to provide a great neighborhood public school for every student in every Zip code.”

“As president, he is committed to attracting and retaining the best educators by paying them as the professionals that they are as well as increasing funding for support staff and paraprofessionals,” she continued. “And Biden will fire Betsy DeVos and replace her with an Education secretary who comes from a public-school classroom and believes that educators must have a seat at the table when crafting education policy.”

The NEA’s Saturday vote effectively concludes a nearly yearlong endorsement process, and its decision to back Biden now, on the eve of his first one-on-one debate with Bernie Sanders, is significant. Union leadership has likely concluded that Biden’s front-runner status is about to become permanent.

The endorsement also comes relatively late in the cycle compared with the strategies of other unions. The American Federation of Teachers, the nation’s second-largest educators’ union, jointly endorsed Biden, Bernie Sanders, and Elizabeth Warren in February. Its president, Randi Weingarten, later endorsed Warren in an individual capacity days later.

Both Biden and Sanders already enjoy substantial labor support. Earlier this March, Biden announced that he’d earned the endorsements of UNITE HERE and United Food and Commercial Workers locals in Michigan, Mississippi, Florida and Illinois. By that point, the former vice-president had also drawn the support of a number of Retail, Wholesale, and Department Store Union locals, and the formal endorsement of the International Brotherhood of Electrical Workers Union, among others. Sanders, meanwhile, has earned plenty of labor support too, including endorsements from the American Postal Workers Union and National Nurses United and a number of powerful locals belonging to the AFT, UNITE HERE and the American Federation of State, County, and Municipal Employees.

Endorsements are important, but they don’t always guarantee that a union’s rank-and-file members will vote the same way as their leaders. Sanders won the Nevada Democratic caucuses in no small part because members of the state’s powerful Culinary Union defied their leadership, who did not endorse a candidate but campaigned against Sanders and Elizabeth Warren over their support for Medicare for All. Teachers are also a consistent source of major donor support for Sanders. HuffPost reported in February that while Biden led an internal AFT poll in tandem with Warren, teachers are Sanders’s top donors by profession. At the time, Warren was the second most popular beneficiary of their financial support, and Biden was third.

This post has been updated to clarify the nature of the NEA’s recommendation to members.