Asked about his health directly at the debate on Tuesday night, Mr. Sanders nodded to the rally and to the “special guest.”

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“Let me invite you all to a major rally we’re having in Queens,” he said. “We’re going to have a special guest at that event, and we are going to be mounting a vigorous campaign all over this country.”

He also said, “I’m feeling great.”

Mr. Sanders’s campaign is billing the New York rally as his official return to the campaign trail. It had toyed with holding the rally in Prospect Park in Brooklyn, according to an aide, but settled on a park in Queens, with a backdrop of the Manhattan skyline.

Presidential endorsements from the congresswomen, both members of the group of first-term Democratic women of color known as “the squad,” were highly coveted. In addition to being among the country’s most prominent progressives, the members of the group — Ms. Ocasio-Cortez, Ms. Omar, Representative Rashida Tlaib of Michigan and Representative Ayanna S. Pressley of Massachusetts — have also become some of President Trump’s favorite foils.

Assorted news reports said that Ms. Tlaib planned to endorse Mr. Sanders as well, and early Wednesday Ms. Omar tweeted that Ms. Tlaib was backing him.

Ms. Tlaib’s team did not respond to requests for comment, and Mr. Sanders’s aides did not confirm that Ms. Tlaib had endorsed him.

In a statement, an aide to Ms. Pressley said: “Ayanna has tremendous respect for her sisters-in-service. Ultimately, these political decisions are made as individuals. Ayanna knows that taking back the White House in 2020 is a top priority, and she is working everyday to hold this Administration accountable.”