Two days after Rabbi Elliot Cosgrove delivered a sermon urging congregants to vote against Zohran Mamdani, rabbis across the country were asked to sign a letter quoting him.

By the time it was published Wednesday, 650 rabbis and cantors had done so, adding their names calling out the “political normalization” of anti-Zionism among figures like Mamdani, the New York City mayoral frontrunner.

By Friday, the letter had more than 1,000 signatories, making it one of the most-signed rabbinic letters in U.S. history.

But Cosgrove, the senior rabbi of Park Avenue Synagogue on the Upper East Side, was not one of them.

“As a policy, I do not sign group letters,” he said in an interview.

“My fear of such letters is they can flatten subjects and reduce complex issues to ‘Who’s on a letter and who

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