“Like the vast majority of American Jews, J Street is outraged by the Trump administration’s disgraceful, inhumane treatment of migrants and refugees — and supportive of members of Congress like Representative Ocasio-Cortez who are strongly challenging the president’s hateful policies,” the group said in a statement.

“The legacy of the Holocaust absolutely compels us to act in defense of vulnerable and targeted minorities — and to stop their mistreatment before it grows even worse,” the statement continued. “Instead of policing terminology, we should be doing everything we can to shut down these camps and to aid the families who are imprisoned in them.”

But at least one Democrat, Representative Josh Gottheimer of New Jersey, who lost family members in the Holocaust, criticized Ms. Ocasio-Cortez’s remarks.

“As an American, I’m deeply concerned about the treatment of children at our borders,” Mr. Gottheimer said in a text. “But, make no mistake, the comparison is cruel and disrespectful to the six million who were murdered in the Holocaust, including members of my own family. Concentration camps were places where Jews and others were enslaved, tortured, and then sent to gas chambers to be murdered.”

The comments also set off intense debate over the meaning of the words “concentration camp” and whether the term could be appropriately used to describe anything other than Nazi death camps.

Politicians and public officials generally regard invoking Nazi comparisons as the third rail of politics; it is done at one’s own peril. Sean Spicer, who served as Mr. Trump’s first White House press secretary, was excoriated when he suggested that President Bashar al-Assad of Syria was guilty of acts worse than Hitler and referred to Nazi death camps as “Holocaust centers.”

But Ms. Ocasio-Cortez, 29, is typically intentional about her word choice, as she herself made clear when she addressed her Instagram followers on Monday evening in one of her regular unscripted videos.