Biden Drops Out of Race, Scrambling the Campaign for the White House

President Biden on Sunday abruptly abandoned his campaign for a second term under intense pressure from fellow Democrats and threw his support to Vice President Kamala Harris to lead their party in a dramatic last-minute bid to 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,” Mr. Biden 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.”

Mr. Biden then posted a subsequent online message endorsing Ms. Harris. “My very first decision as the party nominee in 2020 was to pick Kamala Harris as my Vice President,” he wrote. “And it’s been the best decision I’ve made. Today I want to offer my full support and endorsement for Kamala to be the nominee of our party this year. Democrats — it’s time to come together and beat Trump. Let’s do this.”

The president’s decision upended the race and set the stage for a raucous and unpredictable campaign unlike any in modern times, leaving Ms. Harris just 107 days to consolidate support from Democrats, establish herself as a credible national leader and prosecute the case against Mr. Trump. Recent polls have shown her competitive with and even slightly ahead of Mr. Trump.