In 2008, Mr. Carney was still at Time, which, like many mainstream news publications was bleeding cash and staff.

The day after Mr. Obama’s victory, Mr. Carney called his old friend Antony J. Blinken, a deputy national security adviser and a member of Mr. Carney’s garage band, to inquire about a job in the administration. He was eagerly accepted into the vice president’s press office, where he served as communications director, and later chief spokesman, for Vice President Joseph R. Biden Jr.

“You always wonder about someone coming in from the press side,” Mr. Blinken said. “They bring certain obvious advantages, including a deep institutional and personal knowledge of the media and being able to put themselves in the minds of the people covering the White House. But you have the question mark how is this person going to adjust to being on the other side?” But, he added, “What struck me was how quickly and effectively Jay plunged into his new role, his ability and the energy he put into in defending the vice president.”