“Ruffles and Flourishes” played at the start of a White House event on Monday, but in a musical reminder of the transformed presidential race, the blaring horns were not followed by “Hail to the Chief.”

Vice President Kamala Harris, not a still-recovering Joe Biden, walked onto a South Lawn stage one day after the president ended his bid for a second term and threw his support behind her. Democrats continued to rally around Harris — in the forms of donations and endorsements — to be the party’s presidential nominee, shaking up a race in which Biden had been losing ground to former President Donald Trump.

“It changes everything about the campaign. It’s a whole new day,” Ivan Zapien, a former DNC official and Senate aide, said in a Monday email. “It’s a boxing match on top of the Millenium Falcon in ‘Star Wars’ as Chewbacca hits warp speed.”

Later Monday, during a stop at her campaign headquarters in Wilmington, Del., Harris went right at Trump as she used what amounted to her first speech as the party’s likely nominee to allude to her time as a prosecutor in California.

“I took on perpetrators of all kinds. Predators who abused women. Fraudsters who ripped off consumers. Cheaters who broke the rules for their own gain,” she said to applause from staff there. “So hear me when I say I know Donald Trump’s type. And in this campaign, I will proudly … put my record against his.”

The campaign is about “two different visions for 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 back to a time when many of our fellow Americans” lacked many freedoms or rights. 

She vowed to strengthen the middle class, enact stricter firearms background checks and “fight for reproductive freedom,” contending Trump would sign a national abortion ban. “When Congress passes a law to restore reproductive freedoms, as president of the United States, I will sign it into law,” she said.

The vice president had been working the phones since Biden announced his decision to “stand down,” on Sunday alone calling more than 100 party bigwigs, lawmakers, governors, labor leaders and civil rights advocates, according to a person familiar with her efforts. That outreach continued Monday, and Harris made her first public appearances since becoming the Democratic front-runner.

“Joe Biden’s legacy of accomplishments over the past three years is unmatched in modern history,” she said during an event honoring NCAA champions at the White House. “In one term, he has already surpassed the legacy of most presidents who have served two terms in office.”

To the athletes assembled on the South Lawn, she delivered a message that also could serve as advice for her own likely campaign against Trump, again the GOP nominee: “I know it was not easy to make it to this moment. Each of you has faced challenges and obstacles, and you have endured. … By doing so, you demonstrated that true greatness requires more than skill.  It requires grit and determination.”

The vice president stood in at the event for Biden, who has completed antiviral treatment for COVID-19 at his Delaware home, according to his doctor. Hours earlier, three potential rivals for the nomination — Kentucky Gov. Andy Beshear, Illinois Gov. JB Pritzker and retiring West Virginia Sen. Joe Manchin III — said they would not run. Former Speaker Nancy Pelosi, D-Calif., who reportedly had pleaded with Biden in recent days to consider dropping out, also endorsed Harris on Monday, offering her “enthusiastic support.”

Senate Majority Leader Charles E. Schumer and House Minority Leader Hakeem Jeffries, both of New York, had not formally backed Harris. But in a joint statement released Monday afternoon, the duo said she was “off to a great start with her promise to pursue the presidential nomination in a manner consistent with the grassroots and transparent process set forth by the Democratic National Committee.” They added they planned to meet with her “shortly as we collectively work to unify the Democratic Party and the country.”

Harris had garnered the backing of enough delegates to clinch the Democratic Party’s nomination, according to a survey by The Associated Press, as of 9:45 p.m. on Monday. She secured a majority of the 3,649 delegates as it was announced she won the backing of Georgia’s delegation.

“Georgia Democrats know that Vice President Harris is the right candidate to defeat convicted felon Donald Trump – we are united, our eyes are on the prize, and we’re ready to send her back to the White House as President,” Rep. Nikema Williams, who is chair of the Democratic Party of Georgia, said in a statement.

What’s more, the Harris campaign announced it had raked in $81 million since Biden bowed out, via 880,000 “grassroots donors.” Sixty percent of those donations came from individuals making their first contributions of the 2024 election cycle, the campaign added. 

Some potential rivals appeared to be auditioning to be her second in command.

“I’m excited to fully endorse Vice President Harris for the next president of the United States. The vice president is smart and strong, which will make her a good president,” Beshear said in a television interview, before taking a swipe at Trump and his running mate, Sen. JD Vance of Ohio. “But she’s also kind, and has empathy, which can make her a great president. And the contrast between her and those running on the other side couldn’t be clearer.”

A RealClearPolitics average of multiple national and battleground polls showed Harris polling better against Trump, but only by a few points each. Still, Sen. Amy Klobuchar of Minnesota, a 2020 Democratic primary foe of Biden and Harris, told MSNBC there is “excitement” within her party the likes of which she has never experienced.

Harris atop the Democratic ticket would immediately alter the tone of the race, as well as the tactics both sides will employ. Here’s a look at how the campaign likely would differ from a Biden vs. Trump rematch.

Abortion access

A number of influential Democrats mentioned abortion access and Harris being the campaign’s and White House’s leading voice as an issue that likely will have a bigger role with her as the probable nominee.

“Officially, I have seen Kamala Harris’s strength and courage as a champion of working families, notably fighting for a woman’s right to choose,” Pelosi said in a statement. “Politically, make no mistake, Kamala Harris as a woman in politics is brilliantly astute — and I have full confidence that she will lead us to victory in November.”

Mini Timmaraju, president and CEO of Reproductive Freedom for All, during a May interview called Harris the Democrats’ “most effective” messenger on abortion. She said that Harris could be a draw with independent voters in the swing states expected to decide the election.

“We know independent voters are movable,” Timmaraju added. “She speaks to this audience really effectively.”

Oldest nominee

When Biden posted his departure letter on social media, the 78-year-old Trump instantly became the oldest major party nominee in U.S. history. Biden’s verbal stumbles, including during a disastrous June 27 debate against Trump, have received more coverage. But Trump in recent months also has slurred his words, frozen on stage and mixed up names of prominent figures.

Harris’ ascension could allow Democrats to argue Trump is too old to serve a four-year term.

Harris on the ticket “might reinvigorate support from young people and nonwhite voters, and her advocacy for the pro-choice cause could lead moderate suburban women to reconsider their presidential choice,” said William Galston, a former Clinton White House aide. 

Still he added, “Harris will need to defend the Biden-Harris administration, important aspects of which the voters don’t like.”

Harris was energetic during the Monday event, smiling as she congratulated the student athletes, and did not appear to utter any flubs as she delivered remarks.

Felon vs. prosecutor

Biden had tried, at times, to score political points on Trump’s criminal conviction after a New York City trial on 34 counts of falsifying business records.

“As a prosecutor, as an attorney general like I used to be, she prosecuted rapists, domestic abusers, stood for victims and put away those abusers. Now look at the other side, where JD Vance calls pregnancy arising from rape ‘inconvenient,’” Beshear told MSNBC. “No, it’s just plain wrong. He suggests that women should stay in abusive relationships. 

“Now, listen, a domestic abuser isn’t a man, he’s a monster,” the Kentucky chief executive added. “And no one should support anyone having to stay in those relationships.”

Biden handing the Democratic baton to Harris plunges not only their party but the presidential contest into the political unknown, Zapien said. But that could be an advantage for the vice president.

“The oddsmakers don’t have much to base their odds on,” he said. “You can bet on Democrats being excited for sure.”

Democrats have made clear they see a better matchup on paper. But, like sports games, elections are played in reality and a lot can happen in four months.

Biden, who had called into campaign headquarters when Harris was there, said he intends to campaign for her.

“I won’t be on the ticket, but I’ll be fully, fully engaged,” the outgoing president said.

After two weeks of Democratic strife, Harris and Biden also had a warmer moment, with Biden  listening on an open telephone line at the beginning of her remarks and saying, “I’m watching you, kid. I’m watching you. I love you.”

A smiling Harris clutched her hands to her suit jacket and returned the affection. To the staff, she said, “We are one team, one fight. … We have some hard work to do.”

Niels Lesniewski contributed to this report.