WASHINGTON – President Biden abandoned his campaign for a second term under intense pressure from fellow Democrats on Sunday, upending the race for the White House in a dramatic last-minute bid to find a new candidate who can stop former President Donald J. Trump from returning to the White House.

“It has been the greatest honor of my life to serve as your President,” he said in a letter posted on social media. “And while it has been my intention to seek re-election, I believe it is in the best interest of my party and the country for me to stand down and to focus solely on fulfilling my duties as President for the remainder of my term.”

Biden, who evidently plans to serve out his term through January even as he pulls out as a candidate, said he would “speak to the nation later this week in more detail about my decision” and expressed thanks to Vice President Kamala Harris “for being an extraordinary partner in all this work.” But he did not immediately endorse her and said nothing about how the Democratic Party should proceed to pick a new nominee.

The president’s decision set the stage for an intense, abbreviated scramble to build a new Democratic ticket, the first time in generations that a nomination will be settled at a convention rather than through primaries. Although he did not endorse Harris, she starts the truncated process in the strongest position, but could face challenges from other Democrats.

While Biden has six more months in office, the transition of the campaign to whomever is chosen will amount to a momentous generational change of leadership of the Democratic Party. The eventual nominee will have just over 75 days after next month’s convention to consolidate support from Democrats, establish themselves as a credible national leader and prosecute the case against the Republican former president.

Biden, 81, announced his withdrawal after a disastrous debate performance against Mr. Trump cemented public concerns about his age and touched off widespread panic among Democrats about his ability to prevent the former president from reclaiming power. Democratic congressional leaders petrified by dismal poll numbers pressed Biden to gracefully exit, angry donors threatened to withhold their money and down-ballot candidates feared he would take down the whole ticket.

No sitting president has dropped out of a race so late in the election cycle in American history, and Harris and any other contenders for the nomination will have just weeks to earn the backing of the nearly 4,000 delegates to the Democratic National Convention. While the convention is scheduled to take place in Chicago from Aug. 19 to Aug. 22, the party had already planned to conduct a virtual roll call vote before Aug. 7 to ensure access to ballots in all 50 states, leaving little time to assemble support.

Biden’s campaign for a second term collapsed in swift and stunning fashion after leading Democrats concluded that he would be unable to defeat Mr. Trump in the fall. During their nationally televised debate last month, Biden, the oldest president in American history, appeared frail, hesitant, confused and diminished, losing a critical opportunity to make his case against Trump, a convicted felon who tried to overturn the last election. (The New York Times)…[+]