A Fumbling Performance, and a Panicking Party

President Biden hoped to build fresh momentum for his re-election bid by agreeing to debate nearly two months before he is to be formally nominated. Instead, his halting and disjointed performance on Thursday night prompted a wave of panic among Democrats and reopened discussion of whether he should be the nominee at all.

Over the course of 90 minutes, a raspy-voiced Mr. Biden struggled to deliver his lines and counter a sharp though deeply dishonest former President Donald J. Trump, raising doubts about the incumbent president’s ability to wage a vigorous and competitive campaign four months before the election. Rather than dispel concerns about his age, Mr. Biden, 81, made it the central issue.

Democrats who have defended the president for months against his doubters — including members of his own administration — traded frenzied phone calls and text messages within minutes of the start of the debate as it became clear that Mr. Biden was not at his sharpest. Practically in despair, some took to social media to express shock, while others privately discussed among themselves whether it was too late to persuade the president to step aside in favor of a younger candidate.

“Biden is about to face a crescendo of calls to step aside,” said a veteran Democratic strategist who has staunchly backed Mr. Biden publicly. “Joe had a deep well of affection among Democrats. It has run dry.”

“Parties exist to win,” this Democrat continued. “The man on the stage with Trump cannot win. The fear of Trump stifled criticism of Biden. Now that same fear is going to fuel calls for him to step down.”

A group of House Democrats said they were watching the debate together, and one, who spoke on the condition of anonymity, acknowledged that it was a “disaster” for Mr. Biden. The person said the group was discussing the need for a new presidential nominee.