As a groundswell of criticism threatened to capsize her appointment as New York City’s schools chancellor, Cathleen P. Black, a publishing executive with no background in education policy, was increasingly focused on one question: What would Oprah say?

Eager for Oprah Winfrey to offer a testimonial on her behalf, Ms. Black dispatched a deputy mayor to broker an endorsement through Gayle King, a mutual friend. Later, Ms. Black went as far as to suggest talking points for the television star to keep in mind when describing the would-be chancellor.

“Tremendous leadership, excellent manager, innovator, mother of two and cares about the future of all children,” Ms. Black wrote in an e-mail to Ms. Winfrey on Nov. 17, 2010. “Grace under pressure.” She ended the message: “I owe you big time.”

The exchange was revealed on Thursday after the Bloomberg administration lost a legal battle to withhold a series of e-mail exchanges between Ms. Black and city officials, which the city had fought for two years to keep private.