WASHINGTON >> President Joe Biden abandoned his floundering reelection bid on Sunday under growing pressure from his fellow Democrats and endorsed Vice President Kamala Harris to replace him as the party’s candidate to face Republican Donald Trump in the November election.

Biden, who at 81 is the oldest person ever to have occupied the Oval Office, said he will remain in his role as president until his term ends on Jan. 20, 2025, and will address the nation this week. He has not been seen in public since testing positive for COVID-19 last week and is isolating at his home in Rehoboth Beach, Delaware.

“While it has been my intention to seek reelection, 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 wrote on X.

The move dramatically reshapes a White House contest that has been shaken repeatedly in the last month, including by Biden’s disastrous June 27 debate performance – which drove his fellow Democrats to urge him to drop out – the July 13 attempted assassination of former President Trump, 78, and Trump’s naming last week of hardline Republican U.S. Senator J.D. Vance, 39, to serve as his vice presidential running mate.

In opinion polls, Americans had expressed widespread dissatisfaction over a potential Biden-Trump rematch. Trump told CNN on Sunday that he believed Harris would be easier to defeat.

If Harris emerges as the nominee, the move would represent an unprecedented gamble by the Democratic Party: its first Black and Asian American woman to run for the White House in a country that has elected one Black president and never a woman president in more than two centuries.

Democratic National Committee Chair Jaime Harrison said the American people will soon hear from the party on next steps and the path forward for the nomination process. It was the first time in over a half-century that an incumbent U.S. president gave up his party’s nomination.

If officially nominated, Harris, 59, would become the first Black woman to lead a major-party ticket in U.S. history. A former attorney general of California and former U.S. senator, she ran unsuccessfully for president against Biden in 2020.

“My intention is to earn and win this nomination,” Harris said in a statement. “I will do everything in my power to unite the Democratic Party — and unite our nation — to defeat Donald Trump.”

Harris campaign officials, allies and supporters have started making calls to secure the support of delegates for her nomination ahead of the Democratic National Convention in Chicago from Aug. 19-22, multiple sources said.

Opposition to Biden’s continued campaign from within his party gained steam over the past week with 36 congressional Democrats – more than one in eight – publicly calling on him to drop out, driven by concerns over his mental acuity.

Lawmakers said they feared he could cost them not only the White House but also the chance to control either chamber of Congress next year, which would leave Democrats with no meaningful grasp on power in Washington.

That stood in sharp contrast to what played out in Milwaukee last week, when Republican convention delegates united around Trump, whose refusal to acknowledge his 2020 loss to Biden sparked the Jan. 6, 2021, assault on the U.S. Capitol.

Pennsylvania Governor Josh Shapiro, one of a handful of Democrats seen as potential vice presidential material, on Sunday endorsed Harris’ bid for the nomination. Others, including Governors Gavin Newsom of California, Gretchen Whitmer of Michigan and Andy Beshear of Kentucky, issued statements praising Biden that did not mention Harris.

LAST-MINUTE SHIFT

Biden had a last-minute change of heart, said a source familiar with the matter. The president told allies that as of Saturday night he planned to stay in the race before changing his mind on Sunday afternoon.

“At around 1:45 p.m. today: the president told his senior team that he had changed his mind,” the source told Reuters, speaking on condition of anonymity. Biden announced his decision on social media within minutes after that.

It was unclear whether other senior Democrats would challenge Harris for the nomination – she was widely seen as the pick for many party officials – or whether the party itself would choose to open the field for nominations.

Polling shows that Harris performs no better statistically than Biden against Trump.

In a hypothetical head-to-head matchup, Harris and Trump were tied with 44% support each in a July 15-16 Reuters/Ipsos poll conducted immediately after the July 13 assassination attempt on Trump. Trump led Biden 43% to 41% in that same poll, though the 2 percentage point difference was not meaningful considering the poll’s 3-point margin of error.

Congressional Republicans argued that Biden should resign the office immediately, which would turn the White House over to Harris and put House of Representatives Speaker Mike Johnson, a Republican, next in line in succession.

“If he’s incapable of running for president, how is he capable of governing right now? I mean, there is five months left in this administration. It’s a real concern, and it’s a danger to the country,” Johnson told CNN on Sunday before Biden’s announcement.

Johnson in a separate interview on ABC signaled that Republicans would likely try to mount legal challenges to Democrats’ move to replace Biden on the ballot.

Biden’s campaign had $95 million on hand at the end of June, according to a Saturday filing with the Federal Election Commission. Campaign finance law experts disagree on how readily that money could be shifted to a Harris-led campaign.

FIRST SINCE LBJ

Biden’s historic move – the first sitting president to give up his party’s nomination for reelection since President Lyndon B. Johnson during the Vietnam War in March 1968 – leaves his replacement with less than four months to wage a campaign.

Biden was the oldest U.S. president ever elected when he beat Trump in 2020. During that campaign, Biden described himself as a bridge to the next generation. Some interpreted that to mean he would serve one term, a transitional figure who beat Trump and brought his party back to power.

But he set his sights on a second term in the belief that he was the only Democrat who could beat Trump again amid questions about Harris’s experience and popularity. In recent times, though, his advanced age began to show through more. His gait became stilted and his childhood stutter occasionally returned.

Donors began to revolt and supporters of Harris began to coalesce around her. Top Democrats, including former House of Representatives Speaker Nancy Pelosi, a longtime ally, told Biden he cannot win the election.

Harris is a former prosecutor, and Trump, who is two decades her senior, faces two outstanding criminal prosecutions related to his attempts to overturn the 2020 election result. He is due to be sentenced in New York in September, having been convicted of trying to cover up a hush-money payment to a porn star.

He has pleaded not guilty to all charges and claims all are politically motivated attempts to block him from returning to power.

Earlier this year, facing little opposition, Biden easily won the Democratic primary race to pick its presidential candidate, despite voter concerns about his age and health.

His staunch support for Israel’s military campaign in Gaza eroded support among some in his own party, particularly young, more liberal Democrats and voters of color.

Many Black voters say Biden has not done enough for them, and enthusiasm among Democrats overall for a second Biden term had been low. Even before the debate with Trump, Biden was trailing the Republican in some national polls and in the battleground states he would have needed to win to prevail on Nov. 5.