Many Democrats have quickly backed Vice President Kamala Harris to run as the party's presidential nominee against Donald Trump after President Joe Biden's abrupt departure from the race, but some powerful party members, including former House of Representatives Speaker Nancy Pelosi, stayed quiet.
After weeks of fighting among Democrats on whether Biden, 81, should stay in the race, a rush of support coalescing behind Harris, if she is to be the nominee, is crucial with just over 100 days before the November election.
But there are plenty of doubts inside the Democratic Party about whether Harris can beat Trump, the Republican nominee and former president.
Some Democrats have suggested the party should hold a mini-primary before the August convention.
Biden himself endorsed Harris, in a separate statement following his letter saying that he is stepping down.
He was quickly followed by the powerful Congressional Black Caucus, several key donors, various lawmakers and super PACs including Priorities USA and Unite the Country.
"Today I want to offer my full support and endorsement for Kamala to be the nominee of our party this year," Biden said on social media platform X. "Democrats — it's time to come together and beat Trump. Let’s do this."
The list of Democratic lawmakers endorsing Harris grew as the day progressed.
By Sunday evening, the list included California Governor Gavin Newsom, Colorado Governor Jared Polis, North Carolina Governor Roy Cooper, Pennsylvania Governor Josh Shapiro, Senator Mark Kelly of Arizona, Senator Patty Murray of Washington state, Representative James Clyburn of South Carolina, and Representative Pramila Jayapal of Washington.
Dmitri Mehlhorn, an adviser to Reid Hoffman, the LinkedIn founder and a major Democratic donor, called Harris "the American dream personified," noting she is the daughter of immigrants.
"She is also toughness personified, rising from my home town of Oakland California to become the top prosecutor of the state. With Scranton Joe stepping back, I cannot wait to help elect President Harris."
All 50 Democratic party state chairs will support Harris as the party's new presidential nominee, Reuters reported, citing multiple sources.
The Democratic delegations to the nominating convention from Tennessee, Louisiana, South Carolina and North Carolina said they support Harris.
Former President Bill Clinton and Hillary Clinton, who served as secretary of State under President Barack Obama, also endorsed Harris in a statement.
Still, others, including Pelosi and Obama, under whom Biden served as vice president for eight years, thanked Biden for his patriotism but did not yet throw their support behind Harris or any other candidate.
"We will be navigating uncharted waters in the days ahead," Obama said in a statement. "But I have extraordinary confidence that the leaders of our party will be able to create a process from which an outstanding nominee emerges."
Just as he did in 2020 once Biden earned the Democratic nomination, Obama believes he will be uniquely positioned to help unite the party once it has a nominee, said a source familiar with the matter.
Senate Majority Leader Chuck Schumer, who praised Biden's decision to step aside, also was silent on who should be the Democrats' nominee.
US Senator Peter Welch, the first Democratic senator to call on Biden to drop his reelection run, called for an open nomination process.
The Democrats should have "an open process so that whoever our nominee is, including Kamala, has the strength of having a process that shows the consensus position of the party," Welch said. "The debate in the Democratic Party is who can carry on the legacy of President Biden and defeat Trump."
One Democratic donor told Reuters they would support a ticket for Harris as the presidential candidate and Pennsylvania Governor Josh Shapiro as her vice president, as a way to gain votes in Pennsylvania, a critical swing state. It is not known yet whom Harris would pick as her vice president if she does become the nominee.
And a group appealing to supporters of former Republican presidential candidate Nikki Haley who had been backing Biden under the name Haley Voters for Biden, changed its name on Sunday to Haley Voters for Harris.
Trump told CNN on Sunday that he believed Harris would be easier to defeat.
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.
"Last night the message was proceed with everything, full speed ahead," the source told Reuters, speaking on condition of anonymity. "At around 1:45 p.m. today: the president told his senior team that he had changed his mind."
Biden announced his decision on social media within minutes.
It was unclear whether other senior Democrats would challenge Harris for the party's 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.
Public opinion 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.
Republicans questions Biden's capacity to stay in power
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 announcement follows a wave of public and private pressure from Democratic lawmakers and party officials to quit the race after his shockingly poor debate.
His troubles took the public spotlight away from Trump's performance, in which he made a string of false statements, and trained it instead on questions surrounding Biden's fitness for another four-year term.
His gaffes at a NATO summit - invoking Russian President Vladimir Putin's name when he meant Ukrainian President Volodymyr Zelenskiy and calling Harris "Vice President Trump" -further stoked anxieties.
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.
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.
A growing number of Democratic US lawmakers backed Harris in the hours after Biden's announcement as the vice president vowed to earn their support, while Republicans were quick to tie her to Biden's agenda and blame her for the crisis at the US southern border and inflation.
"The work is not done; in fact it is just beginning. I proudly and enthusiastically support Vice President Harris, whom I believe is the very best person in this moment to unify the Democratic Party and lead us forward to victory," Democratic US Senator Tina Smith wrote on X.
Biden was the oldest US president ever elected when he beat Trump in 2020. During that campaign, Biden described himself as a bridge to the next generation of Democratic leaders. 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.
His team had hoped a strong performance at the June 27 debate would ease concerns over his age. It did the opposite: a Reuters/Ipsos poll after the debate showed that about 40% of Democrats thought he should quit the race.
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.
Biden's departure sets up a stark new contrast, between the Democrats' presumptive new nominee, Harris, a former prosecutor, and Trump who is two decades her senior and 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 on a conviction for trying to cover up a hush-money payment to a porn star.
Biden struggled before debate
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, progressive Democrats and voters of color, who make up an essential part of the Democratic base.
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.
Harris was tasked with reaching out to those voters in recent months.
During the primary race, Biden accumulated more than 3,600 delegates to the Democratic National Convention to be held in Chicago in August. That was almost double the 1,976 needed to win the party's nomination.
Unless the Democratic Party changes the rules, delegates pledged to Biden would enter the convention “uncommitted," leaving them to vote on his successor.
Democrats also have a system of “superdelegates," unpledged senior party officials and elected leaders whose support is limited on the first ballot but who could play a decisive role in subsequent rounds.
Biden beat Trump in 2020 by winning in the key battleground states, including tight races in Pennsylvania and Georgia. At a national level, he bested Trump by more than 7 million votes, capturing 51.3% of the popular vote to Trump's 46.8%.
