Offstage, a Band of Biden Defenders Braves a Sea of Trump Swagger

The job was to spin, and they had their work cut out for them.

In the minutes after the presidential debate ended on Thursday night, a cluster of Democrats walked into the spin room to defend their candidate, an 81-year-old president who showed up after a week of debate preparations with a hoarse voice, a head swimming with facts and figures, and an inability to contain the reality-bending and often fact-free bluster of his opponent, Donald J. Trump.

For much of the debate, Mr. Biden looked down, or looked wide-eyed and slack-jawed, absorbing what was happening, angry but unable to hit back. At times he spoke into a microphone that had been cut off according to debate rules his team had outlined.

So it was a bit of an uphill climb. The crew had the difficult job of trying to promote the policies the president tried but often failed to espouse, without calling attention to the one thing Mr. Biden could not outrun: his age.

“I would never turn my back on President Biden’s record,” Gov. Gavin Newsom of California said, when asked whether he supported the whispers — swiftly rising to a shriek — among some Democrats who believed Mr. Biden’s performance was bad enough to warrant being struck from the ticket. He added: “I was very proud of the president.”

And on went the sober scene among the small clutch of surrogates, who were all clearer messengers for the president’s policies than Mr. Biden himself had been over the course of more than 90 minutes onstage.

The Trump side beat them to the floor by several minutes, and at least a dozen surrogates were swaggering. Lara Trump, the co-chairwoman of the Republican National Committee, said that, from what she had seen, “it was very clear” that the theme of the debate was “strength versus weakness.”