The Democratic Party largely coalesced around Vice President Kamala Harris as its likely new presidential nominee today, as she kicked off her campaign by promising to prosecute a forceful case against Republican nominee Donald Trump and defend the legacy of President Joe Biden.

Hours after she delivered remarks laying out some of the themes of her campaign, Harris secured pledges of support from a majority of Democratic National Convention delegates, a forceful show of unity behind her presidential campaign that signals she is likely to officially become the party’s nominee next month.

“Over the next 106 days, we are going to take our case to the American people, and we are going to win,” Harris said during a visit to campaign headquarters in Wilmington, Delaware, where she was greeted by a group of energised staffers for Biden’s now-abandoned candidacy. Harris accused Trump of wanting to “take our country backwards to a time before many of our fellow Americans had full freedoms and rights.” She added, “we believe in a brighter future that makes room for all Americans.”

Biden dialled into the impromptu meeting, using his first public remarks after dropping out of the presidential race Sunday to thank his staff and ask them to support Harris with “every bit of your heart and soul.”

“The name has changed at the top of the ticket, but the mission hasn’t changed at all,” said Biden, who joined remotely from Rehoboth Beach, where he has been recovering from a case of Covid. “We still need to save this democracy. Trump is still a danger to the community. He’s a danger to the nation.”

The high-energy, highly unified setting reflected the broader sentiment across the Democratic Party, in which Harris’ swift ascendancy has upended an already tumultuous and unpredictable presidential race. After being exhausted by weeks of turmoil and infighting over Biden’s prospects, relieved and newly energised Democrats across the country rushed to embrace Harris’ candidacy and unite around the goal of defeating Trump.

Less than 36 hours after Biden abruptly exited the race and endorsed Harris as his successor, hundreds of state delegates, the majority of Democratic lawmakers and governors, a group of state party chairs, and several influential interest groups threw their support behind Harris, as other potential candidates said they would not challenge her. Top congressional leaders followed suit, with Senate Majority Leader Charles E. Schumer (D-N.Y.), House Minority Leader Hakeem Jeffries (D-N.Y.) and former House speaker Nancy Pelosi (D-Calif.) expressing support for Harris on Monday.

Kamala Harris kicks off her campaign by promising to prosecute a forceful case against Donald Trump. Photo / Getty Images

While a small number of Democrats have advocated an open, competitive process, Harris appeared to have an inside track on Monday to quickly securing the nomination ahead of the party’s convention next month.

Harris sought to reflect that sense of unity by using her visit to Wilmington, where she paid tribute to Biden and announced that she had tapped his campaign chair, Jen O’Malley Dillon, to run her presidential bid.

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“I am a firsthand witness from being with him in the Oval Office, to the Situation Room and seeing him on the global stage with world leaders,” Harris told staff members, echoing a message she had delivered at the White House earlier in the day. “President Joe Biden fights for the American people, and we are deeply, deeply grateful for his service to our nation.”

But even as Harris was laying out a campaign message focused on defending “freedoms,” the Trump campaign was gearing up to launch a full-scale assault against her by describing her as “Dangerously liberal” and a threat to Americans’ fundamental rights.

“This is a new fight for American Independence,” Trump campaign senior advisers Chris LaCivita and Susie Wiles wrote in a memo that attacked Harris over inflation, immigration, electric vehicles and crime.

Trump’s running mate, Sen. J.D. Vance (R-Ohio), went after Harris in his first solo campaign appearances on Monday. At an event in Radford, Va., he criticised Biden as “a quitter” and said that Harris “is a million times worse”.

The memo and Vance’s appearances, which laid out some of the GOP’s main lines of attack on Harris, reflected how much Trump and his allies have been forced to regroup and reorient their strategy in the wake of Biden’s exit. After celebrating the extended infighting and discord that plagued Democrats in the aftermath of Biden’s halting performance at the June 27 debate, Trump’s allies watched Monday as Democratic leaders quickly fell in line behind Harris.

“I’m excited to fully endorse Vice President Harris for the next president of the United States,” Kentucky Gov. Andy Beshear (D) said Monday on MSNBC’s “Morning Joe” program. “The vice president is smart and strong, which will make her a good president, but she’s also kind and has empathy, which can make her a great president.”

Beshear sidestepped questions about whether he was angling to join Harris as a running mate, though he notably used his appearance to attack Vance, a kind of public audition that he and other top Democrats are engaging in as the party begins to shift its focus to who will share the ticket with Harris.

Joe Biden has dropped out of the presidential race. Photo / Getty Images

Democratic Govs. Gretchen Whitmer of Michigan, J.B. Pritzker of Illinois and Wes Moore of Maryland also endorsed Harris on Monday, joining a growing list of potential rivals for the nomination that instead opted to endorse her candidacy. Govs. Gavin Newsom of California and Josh Shapiro of Pennsylvania, each considered potential candidates, both endorsed Harris on Sunday.

Democratic leaders on Monday unveiled a new virtual process for selecting a nominee to replace Biden that would conclude by August 7, ahead of the nominating convention in Chicago next month. The dates for the virtual process will be announced on Wednesday.

The private doubts about Harris’ vulnerabilities and less-than-impressive polling numbers largely remained unspoken Monday as Democrats appeared eager to consolidate around a candidate and head off a messy competition for the nomination 106 days before the November 5 election. During her visit to campaign headquarters in Wilmington, Harris was greeted by more than 100 staff members who gave her a standing ovation. The room was covered in newly printed signs that read “Harris for President,” though at least one lingering “Biden-Harris” sign stood as a testament to how rapidly the presidential race had shifted.

Campaign aides said more than 28,000 new volunteers had signed up to lend support, more than 100 times the typical number. Harris, who has been travelling around the country, planned to continue her campaign travel this week.

Trump had built an advantage in polls of key swing states and has at times appeared frustrated with Biden’s exit from the race, lamenting Sunday that he had to “start all over again” after long focusing on Biden. In a social media post Monday, Trump who often relies on insults and name-calling, called Harris “Dumb as a Rock.” The Republican National Committee’s research account on X - long accustomed to circulating clips of Biden looking old or confused - began attacking Harris during her speech to NCAA championship teams from the 2023-2024 season.

The turn of events resulted in a rare instance of Harris hosting a White House gathering on the South Lawn by herself, a privilege typically reserved for presidents. While the sports-focused gathering was designed to be lighthearted and low-pressure, many were watching to see how Harris performed in a presidential role. During brief remarks, she called herself “a firsthand witness” to how Biden “fights for the American people.”

Harris’ nascent campaign has tried to frame the rush of endorsements as a sign of her hard work to unify and energise the party.

Harris’s operation raised a record $81 million in the first 24 hours after Biden dropped out and endorsed his vice president, aides said. A group of tens of thousands of Black women gathered on a virtual call Sunday evening to showcase their support for Harris’ bid to become the first woman of colour to be president.

Harris spent more than 10 hours on the phone on Sunday, wearing a hoodie and sweatpants, calling dozens of officials across the country to secure their support, according to a person familiar with the situation, who spoke on the condition of anonymity to discuss the internal process.

The rapid political embrace of Harris marked a notable shift from a party that had previously questioned her strengths as both a candidate and as a vice president.

Last year, multiple commentators called for Harris to be swapped out as Biden’s running mate, and several leading Democrats struggled on live television to answer what had become a hot-button question: Is Harris the best option for vice-presidential candidate?

“He thinks so, and that’s what matters,” Pelosi said on CNN in September, referring to Biden in what was widely interpreted as a non-committal answer. Sen. Elizabeth Warren (D-Mass.) and Rep. Jamie Raskin (D-Md.) also offered less than enthusiastic support for Harris last year during television interviews. All three have now endorsed Harris’ bid to be the nominee.

Still, there were notable holdouts. Former president Barack Obama released a statement on Sunday praising Biden without explicitly endorsing Harris, asserting that Democrats would ultimately find “an outstanding nominee.”

Sen. Joe Manchin III (I-W.Va.) initially expressed interest in challenging Harris for the nomination, before taking himself out of the running on Monday. Manchin, who left the Democratic Party in May to become an independent, said he wanted the party to embrace an open process to allow more-moderate candidates to compete. Before Biden left the race on Sunday, Manchin suggested in an interview with The Washington Post that Harris was too liberal.

“I think we can rebuild the Democratic brand and right now you’re going to have to pick somebody that physically and mentally basically believes with every fibre of their body that we’ve gone too far to the left,” he said. “Now if they don’t, they’re going to keep dwindling away.”

Former New York mayor Mike Bloomberg, who sought the Democratic nomination in 2020, warned the party against rapidly lining up behind any candidate before taking “the pulse of voters.”

“The decision is too important to rush, because the election is too important to lose,” he wrote Monday on X.

In a new ad released hours after Biden dropped out, the Trump campaign targeted Harris over the surge of migration at the southern border, falsely branding her the nation’s “border czar.” The ad featured a repeated clip of Harris laughing, part of an attempt by Trump to undermine her bid to be commander-in-chief. At a rally on Saturday, Trump referred to Harris as “laughin’ Kamala” and “crazy,” repeating his practice of mispronouncing her name.

Harris has already begun leaning into her background as a prosecutor and state attorney general as she began to cast the race against Trump in a new light.

“In those roles I took on perpetrators of all kinds,” she said. “Predators who abused women, fraudsters who ripped off consumers, cheaters who broke the rules for their own gain. So hear me when I say I know Donald Trump’s type.”

By dropping out and endorsing Harris, Biden has upended an already unwieldy presidential contest, making the race akin to a sprint rather than a traditional marathon, said Russell Riley, a presidential historian at the University of Virginia’s Miller Center.

“Everything is abbreviated - so what we need to look for is the equivalent of sprinter’s skills,” he said.

“Durability is much less an issue than quick reactions, ability to focus, a fast start and getting into stride quickly.”