American Unions Long Backed Israel. Now, Some Are Protesting It.

“Why are we here?” said Brandon Mancilla, a leader with the United Automobile Workers. Mr. Mancilla faced a crowd of hundreds of union members gathered on the steps of the New York Public Library’s Fifth Avenue branch, huddling against the cold as they rallied for a cease-fire in Gaza.

“Cease-fire now, solidarity forever!” Mr. Mancilla, 29, said as the crowd cheered, waving union banners and Palestinian flags. “Let’s get more and more unions behind us.”

On display in that Dec. 21 protest — which came shortly after the 350,000 member U.A.W. voted to support a cease-fire — was a shift in the American labor movement’s relationship with Israel.

For decades, the most prominent American unions were largely supportive of Israel. Today, though, amid a resurgence of the American labor movement, some activists are urging their unions to call for an immediate cease-fire in Gaza and succeeding — a change that reflects a broader generational shift.

But many unions are divided over what stance to take or whether to take any stance at all.

Some American labor leaders have remained supportive of Israel’s war against Hamas, and moved swiftly to condemn Hamas’s attacks on Oct. 7. They are dismayed by the views of a younger generation of organizers who in some cases oppose Israel’s existence as a Jewish state.

“There has been a shift in society, and that’s reflected in the labor movement as it is every place else,” said Stuart Appelbaum, president of the Jewish Labor Committee and head of the Retail, Wholesale and Department Store Union.