Kamala Harris - and Democrats - face an unprecedented task with 100 days to election

When Joe Biden addressed the NAACP convention in Las Vegas last week, one of his biggest applause lines - a line that set off chants of "Four more years!" - was when he praised Kamala Harris as "not only a great vice-president" but someone who "could be president of the United States".

Now she has that chance.

On Sunday, when the president made the extraordinary decision to end his re-election campaign, he made an equally momentous choice: to offer his "full support and endorsement" of Harris to be the Democratic nominee and take on Donald Trump in November.

"It's time to come together and beat Trump," the 81-year-old president said. "Let's do this."

The announcement, just weeks before the Democrats are set to formally choose their nominee at the convention in Chicago, has plunged an already tumultuous contest deeper into unchartered waters - while thrusting his would-be successor into the spotlight.

"I am honored to have the president's endorsement and my intention is to earn and win this nomination," Harris said. "I will do everything in my power to unite the Democratic party - and unite our nation - to defeat Donald Trump and his extreme Project 2025 agenda."

With just over 100 days until the November election, the task before her is monumental and unprecedented. An assassination attempt on Trump has united Republicans behind him, and appears to have strengthened his hand as Democrats dissolved into a rancorous debate over Biden's fitness to serve.

The question of who would replace Biden has consumed Democrats and party strategists, allowing for an intense public discussion over whether Harris would be the strongest candidate to defeat Trump in November.

The US-born daughter of immigrants, Harris spent much of her career as a prosecutor, before becoming California's attorney general, overseeing the nation's second largest justice system. In 2016, she was elected to the US Senate, becoming the first south Asian American and only the second Black woman to serve in the chamber, where she distinguished herself for asking tough questions of Trump-era political nominees.

Many of Harris's supporters say she is the obvious heir apparent to Biden. She is also the administration's strongest messenger on abortion rights, a top issue for many voters, especially women.

But her skeptics point to her failed 2019 bid for the Democratic nomination, which lacked cohesion and vision, and her shaky start to the vice-presidency, which opened her to withering Republican criticism. Some Democrats are not necessarily opposed to Harris, but believe she would benefit from an open competition - rather than a "coronation" - to prove to party skeptics, donors and voters she is the best candidate for the job.

They say a fast primary campaign would showcase to the American people that Harris is best person for the job, and give would-be contenders a chance to compete - or at least debut as potential running mates.

By anointing Harris, Biden has greatly tipped the scale in her favor. But it does not automatically make her the nominee.

Jaime Harrison, chair of the Democratic National Committee, called the situation "unprecedented" but said the party was committed to carrying out a "transparent and orderly process".

In a remarkable change of course after weeks of infighting, Democrats rushed to throw their support behind Harris, including a wide swath of members of Congress; Hillary Clinton, the first major female presidential nominee; and some would-be opponents like Gavin Newsom, the governor of California; Pete Buttigieg, the secretary of transportation; and Gretchen Whitmer, the Michigan governor. On Monday, Joe Manchin, the one-time Democratic senator turned independent, said he had no plans to vie for the party's presidential nomination.

Harris has a handful of advantages over other potential challengers. She has been vetted at the national level and has good name recognition. As Biden's running mate, she would also likely inherit key parts of his campaign, which includes a large war chest of donor funding and massive field operation.

On Sunday, Biden's campaign fund was renamed "Harris for President", a filing with the Federal Elections Commission showed. As of Saturday, the campaign had nearly $96m cash on hand, according to the FEC. And donors who abandoned Biden in an effort to push him from the race could restart their contributions to a presidential campaign led by a younger candidate.

Harris may also benefit from Democrats' desperate desire to unite quickly and turn the focus back on Trump, whom they view as an existential threat to American democracy.

Trump has repeatedly mocked Harris, assailing her intelligence and her laugh, while mispronouncing her first name. On Sunday, Trump called Harris "as much of a joke" as Biden, and said she had been "complicit" in covering up the president's decline.

"Harris has been the enabler-in-chief for Crooked Joe this entire time. They own each other's records, and there is no distance between the two," he said.

The former president has a history of amplifying racist and sexist conspiracies about Harris, including a birther lie that suggested, falsely, she might be ineligible to serve as president.

The independent candidate Robert F Kennedy also attacked Harris as a "war hawk" on Ukraine and China, and accused her of holding one of the "worst civil rights records of any public official".

Republicans have said they were prepared for a torrent of opposition research on Harris, stemming from her failed 2020 campaign and her years as vice-president.

If the attacks ramp up, they could play on Harris's vulnerabilities. Recent polling that considered a hypothetical matchup between Harris and Trump found her running close to or stronger than Biden nationally and in the battleground states.

Like Biden, Harris is unpopular, though her approval rating has ticked up slightly in the weeks since the party began pressuring Biden to withdraw, following his disastrous debate.

"She's the most unpopular vice-president since Dan Quayle - and Dan Quayle is the most unpopular-vice president since Aaron Burr," Frank Luntz, a pollster and consultant, said recently. Burr, remembered as the vice-president who mortally wounded Alexander Hamilton, served under Thomas Jefferson at the turn of the 19th century.

Harris's supporters say her historic nomination could help inspire and mobilize Democrats who had so far been disillusioned by their options.

Santiago Mayer, executive director of the Democratic-aligned Voters of Tomorrow, said Harris's tour of US college campuses was "incredibly well-received" and helped her understand the unique needs of young people, who polls show are disillusioned with the entire political system.

"We saw the 'Kamalove' that gen Z feels for her and we're incredibly excited to have a younger, more diverse face representing the incredibly successful and pro youth Biden Harris agenda," he said, pointing to the "coconut tree" memes spreading online in an ironic but earnest show of support.

At nearly every stage of her career, Harris has broken barriers, and should she win the nomination, "the nation will watch a multiracial woman compete in a presidential general election for the first time in history," said Debbie Walsh, director of Center for American Women and Politics. "This transformative moment will forever alter how Americans view leadership in politics."

Biden's decision to withdraw, and Harris's commitment to seeking the presidential nomination, means the Democratic ticket is also in need of a vice-presidential candidate. Should Harris be the nominee, several names have been floated including the Arizona senator Mark Kelly, who endorsed the vice-president on Sunday, as well as the governors of Kentucky, Andy Beshear; Pennsylvania, Josh Shapiro, who also endorsed Harris; and North Carolina, Roy Cooper.

Democratic groups had already organized an effort to boost Harris's image and defend her against the Trump attacks that would have come regardless of her position on the ticket. Among them is Way to Win, a Democratic donor network that endorsed Harris.

Tory Gavito, the organization's president and co-founder, said the vice-president performed especially well with young people and voters of color, key constituencies that Democrats have struggled to excite.

With Biden's decision to pass the torch to Harris, she likened the Democratic party to an Olympic sprinter crouching at the starting line.

"All this wait period has just given us that sort of kinetic energy to now run," she said. "And I think it's going to just un-tap a bunch of enthusiasm that gets us ready for November."

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