Both women are among the first-term Democratic women of color known as “the squad.” The other two members of the group, Representatives Rashida Tlaib of Michigan and Ayanna S. Pressley of Massachusetts, have not made a presidential endorsement.

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Continuing the fight with Facebook

In a speech on Thursday at Georgetown University, Mark Zuckerberg, Facebook’s chief executive, argued forcefully against the idea that the social network should be an arbiter of speech, doubling down on a stance that has drawn wide condemnation as the company continues to face accusations of amplifying disinformation.

Ms. Warren renewed that criticism after Mr. Zuckerberg’s speech, saying late Thursday in a tweet: “Facebook is actively helping Trump spread lies and misinformation. Facebook already helped elect Donald Trump once. They might do it again — and profit off of it.”

The comments continued an increasingly public feud between Mr. Zuckerberg and Ms. Warren. Earlier this month, Ms. Warren bought a political ad on Facebook that purposefully included the false claim that Mr. Zuckerberg and Facebook backed Mr. Trump’s re-election — and essentially dared the social network to remove it. (Neither Mr. Zuckerberg nor Facebook has endorsed a candidate.)

Mr. Zuckerberg at one point invoked the Rev. Dr. Martin Luther King Jr. to make his point about free speech, which drew a response from one of Dr. King’s daughters, Bernice King. “I’d like to help Facebook better understand the challenges #MLK faced from disinformation campaigns launched by politicians,” she wrote on Twitter. “These campaigns created an atmosphere for his assassination.”