Rep. Lacy Clay, whose primary challenger Cori Bush won Ms. Ocasio-Cortez’s endorsement, said the initial interview on PBS’s new “Firing Line” program exposed how the political newcomer and other insurgents “are not well-versed on the issues and the subjects that we deal with here in Congress.”

“They are not well versed at all and I think it highlights the differences between people like myself who are progressive Democrats who have a record of results versus a Democratic Socialist who rely heavily on soundbytes with no substance, and no record of results and no pathway to get to real solutions up here,” Mr. Clay said.

With Ms. Ocasio-Cortez scheduled to campaign with his opponent, Mr. Clay said what happened in the Big Apple won’t happen in his political backyard.

“St. Louis, Missouri is not the Bronx, New York,” he said.