Vice President Harris, who is now the presumptive nominee for president, has made clear she will be on the offense for the rest of the campaign. Likening President Trump to the predators, fraudsters, and cheats she once prosecuted, the vice president is articulating a message President Biden was never quite able to. 

Support for Ms. Harris’ candidacy has been overwhelming since Mr. Biden’s departure from the race. Late Monday night, Ms. Harris won the endorsement of the California delegation to the Democratic convention next month. With their 424 votes, Californians delegates have put Ms. Harris over the top to win the nomination at Chicago, making her the second woman in American history to lead the ticket of a major party. Several other state delegations have also voted unanimously to support the vice president. 

Earlier on Monday, Ms. Harris traveled to Wilmington, Delaware to meet at the Biden campaign headquarters, which has now been adorned with California state flags and rebranded as the Harris campaign offices. She met with senior staff to discuss the operation, and announced that Mr. Biden’s campaign manager, Jen O’Malley Dillon — affectionately called “J.O.D.” — would be staying on to lead the Harris campaign. 

During remarks to the campaign staff and the assembled press, she laid into the former president and current Republican nominee as a man not to be trusted by women and hard working Americans. 

As California’s attorney general, and before that a district attorney and line prosecutor, Ms. Harris said she “took on perpetrators of all kinds.” She listed predators who abused women, fraudsters who “ripped off” consumers, and “cheaters who broke the rules for their own gain.”

“Hear me when I say: I know Donald Trump’s type,” eliciting lengthy cheers from the campaign staff. 

“In this campaign, I will proudly put my record against his,” she said. “Donald Trump was found liable by a jury for committing sexual abuse. … Donald Trump ran a for-profit college — Trump University — that was forced to pay $25 million to the students it scammed. … Donald Trump stood at Mar-a-Lago and told big oil lobbyists he would do their bidding for a $1 billion campaign contribution.”

The enthusiasm for Ms. Harris — following the historic decision by Mr. Biden to abandon the campaign — is newsworthy. In just one day, more than 28,000 people signed up to volunteer for the Harris campaign, according to the New York Times, and the vice president raised more than $81 million for her operation. That is apparently trickling down ballot, with USA Today reporting that the Senate Democrats’ campaign arm has tripled their previous one-day grassroots donor record. 

Mr. Biden called into the meeting with Ms. Harris and campaign staff from his Rehoboth beach house, where he has been quarantined with a bout Covid for the better part of a week. Mr. Biden encouraged his most dedicated staff to pat themselves on the backs for what they did for the campaign, and to get to work for his vice president. 

“I’m gonna be on the road. I’m not going anywhere,” Mr. Biden said. Of his vice president, Mr. Biden declared, “I want to say to the team: Embrace her. She’s the best.”

“The name has changed at the top of the ticket, but the mission hasn’t changed at all,” he said. “I’m gonna be working like hell.”

When Ms. Harris took the stage, she thanked elected officials and senior campaign staff for their work, and praised the president for his love of country. 

Early in her remarks, she made clear that the election was not just about Trump’s fitness, but about the agenda she hopes to enact as president. 

“Our campaign has always been about two different versions of what we see as the future of our country,” she said. “One focused on the future, the other focused on the past. Donald Trump wants to take our country backward … But we believe in a brighter future.”

She mentioned an expanded child tax credit, housing affordability, paid family leave and affordable childcare as being among her top priorities. “Together, we fight to build a nation where every person has affordable healthcare,” she declared. 

“Building up the middle class will be a defining goal of my presidency,” she said to cheers.

The Trump campaign is taking note of Ms. Harris’ early successes, and they’re not taking anything for granted despite their current polling lead. In a memo shared with the Sun on Monday, Trump’s two top advisors, Chris LaCivita and Susie Wiles, say they will tie Ms. Harris to “the Biden record of Weakness and Failure.”

Republicans will attack Ms. Harris, the “border czar” as they’ve branded her, for her early decision to try and deal with the underlying issues of immigration flows. “Border Czar Kamala Harris owns the border invasion, which has resulted in nearly 100 terrorists roaming the United States, hundreds of thousands of American dead due to Fentanyl, a child trafficking epidemic resulting in killings and kidnappings, a spread of a new type of crime, a crime directly linked to Harris’ own beliefs,” Mr. LaCivita and Ms. Wiles write. 

The Trump campaign also plans to tie her to the “oppressive weight of the Harris inflation tax,” the “War against American Energy and edicts for all electric cars,” and the “oppressive government hellbent on taking away parental rights.”

The vice president’s campaign has started off strong, to be sure. Every major potential challenger at the Chicago convention next month has already endorsed her to be the nominee, including every Democratic governor, the vast majority of the House and Senate Democratic caucuses, and even Speaker Pelosi. Senator Schumer and Congressman Hakeem Jeffries have so far declined to offer an official endorsement. 

America’s largest labor unions are backing Ms. Harris, as well, including the AFL-CIO, the Communications Workers of America, the Service Employees International Union, and the American Federation of Teachers. 

On Monday, the Democratic National Committee announced the process for choosing its nominee at this year’s convention. Of the nearly 4,000 delegates attending this year, any potential candidates will have to have the support of at least 300 voting members, though candidates may not solicit more than 50 signatures from any one delegation. The chairmen and chairwomen of all 50 state parties have already endorsed Ms. Harris, and some state delegations, including Pennsylvania and Massachusetts, have already pledged their entire delegation to the vice president on the first ballot next month.