LARGO, Md. — President Joe Biden and Vice President Kamala Harris, touting their efforts to lower prescription drug prices for Medicare recipients, hosted their first joint appearance since Biden ended his reelection bid, a policy event that quickly took on the tone and feel of a campaign rally.

Biden and Harris announced agreements on lower drug costs for the first 10 medications selected under a Medicare price negotiation program, including those that treat diabetes, blood clots, heart failure, rheumatoid arthritis and blood cancers.

“As vice president — together with Joe Biden, our president — we’ve finally addressed the long-standing issue that for years was one of the biggest challenges on this subject, which is that Medicare was prohibited by law from negotiating lower drug prices, and that cost was passed on to our seniors,” Harris said. “But not anymore.”

The appearance was billed as an official White House policy event, but it had clear political implications, and Biden leaned into them from the first minute of his remarks. “Folks, I have an incredible partner in the progress we’ve made,” he said, adding, “She’s going to make one hell of a president.”

Harris, for her part, spent much of her speech heaping praise on Biden and his leadership. “I can speak all afternoon about the person that I am standing on the stage with,” she said. “There’s a lot of love in this room for our president, and I think it’s for many, many reasons.”

As the crowd chanted, “Thank you, Joe,” the president brought his hand to his chest and nodded.

The event reflected a complex political moment for the Democratic leaders, as Biden seeks to burnish his legacy while also boosting Harris, and Harris seeks to make the case for her candidacy while honoring Biden. The crowd’s preference was clear, as cheers erupted every time Harris’s name was mentioned, while several dozen attendees sought to leave about 15 minutes into Biden’s remarks.

Among the speakers was Maryland Gov. Wes Moore. “You’re going to hear not just from the 46th president of the United States, Joe Biden, you’re also about to hear from the 47th president of the United States, Kamala Harris,” he said, prompting sustained cheers and screams. The community college venue where the event was held was packed in a way that Biden’s events have rarely been.

Turning to the reason for the event, Biden said he had been fighting since 1973, his first year in the Senate, to give Medicare the authority to negotiate drug prices. If Republicans regained the White House, he added, they would undo the progress his administration had made.

“We finally beat Big Pharma,” he said. “And, might I add, with not one Republican vote in the entire Congress.”

The Inflation Reduction Act, passed in 2022 with Harris casting the tiebreaking vote in the Senate, gave the secretary of health and human services for the first time the power to negotiate with pharmaceutical companies over Medicare drug prices. The administration reported Thursday that the program has resulted in about $6 billion in initial savings.

Biden stressed that Project 2025 — a conservative policy blueprint created for the next GOP administration, which Republican nominee Donald Trump has tried to distance himself from — would strip away Medicare’s ability to negotiate drug prices. “Let me tell you what our 2025 plan is: Beat the hell out of them,” he said.

Harris’s month-old campaign has so far focused on a broad, uplifting message about building a better future, arguing that Trump and Republicans want to take America backward.

Her critics, most notably Trump himself, accuse of her of leaning into partisan rhetoric and the good vibes of a reset campaign while avoiding the details of what she would actually do as president. Harris has not sat down for a formal press interview or news conference, limiting interactions with the media to off-the-record conversations and quick, informal exchanges with reporters.

“We actually have the plans, we have the policies, to accomplish this stuff — that’s a big thing that sets us apart from Kamala Harris and Tim Walz,” Sen. JD Vance (R-Ohio), Trump’s running mate, said at an event in Pittsburgh earlier in the day.

Thursday’s event was in part a response to such criticism, as Harris spoke in detail about the results of a key administration policy. On Friday, she is expected to begin rolling out her own proposals with a speech on the economy, including a plan to ban “price gouging” for food items amid widespread consumer unhappiness over inflation.

Still, detailed policy proposals often come with political risk. Opponents, journalists and even allies will pore over the details of the proposals, looking for negative economic ramifications, unintended consequences and contradictions with Harris’s past stances. Harris will have to publicly defend her policies, including at a Sept. 10 debate between her and Trump.

In an early sign of the back-and-forth to come, Trump hastily scheduled a news conference at his golf club in Bedminster, N.J., for shortly after the Biden and Harris event. He told reporters that some of Harris’s proposals were “communist price controls” that would wreck the economy.

“She wants price controls,” he said in his remarks, which focused on what he described as negative economic indicators since Biden took office, especially inflation. “And if they worked, I’d go along with that. I’d be all for that, but they don’t work. They actually have the exact opposite effect and impact. It leads to food shortages, rationing, hunger, dramatically more inflation.”

As an opening salvo for Harris’s policy rollouts, Democrats see the price reductions on drugs as a potentially winning issue for their candidates across the country, but they face the challenge that few voters know about the issue and the impact of the price cuts will not be felt for years to come.

Democrats have sought to reduce the cost of drug prices in the Medicare program for more than 30 years. Sen. Bernie Sanders (I-Vt.), a former presidential candidate, has campaigned on the issue. But the effort faced immense resistance from a pharmaceutical industry with deep pockets, whose representatives argued that forcing down prices would stifle innovation.

The Biden administration said Thursday the renegotiation will reduce the amount of money that many Medicare beneficiaries have to spend out of pocket. The new, negotiated prices ranged from 38 to 79 percent lower than the drugs’ list prices in 2023, they said, and the initiative is arguably the most significant health-care legislation in more than a decade, since the passage of the Affordable Care Act in 2010.

But the new prices do not take effect until 2026, creating a challenge for Biden and Harris as they seek to make voters aware of major legislation that they say will help them save money.

For nine of the drugs, the negotiations help cut the price by more than 50 percent, officials said. Medicare beneficiaries in 2022 collectively spent $3.4 billion to cover out-of-pocket costs on those drugs, according to a federal analysis released last year. The drugs also represented about one-fifth of the Medicare prescription drug program’s total spending.

Chiquita Brooks-LaSure, administrator of the Centers for Medicare and Medicaid Services, said Medicare enrollees will save an estimated $1.5 billion in 2026, when the new prices take effect. “For so many people, being able to afford these drugs will mean the difference between debilitating illness and living full lives,” she said on a conference call with reporters.

Medicare plans to target 15 additional drugs for negotiations in 2025 and 2026, and 20 drugs in the following years.

Thursday’s joint event offered Democrats an opportunity to use both the presidential bully pulpit and the spotlight from a national campaign to raise awareness of the issue. Harris and her running mate, Minnesota Gov. Tim Walz, are embarking on a bus tour through western Pennsylvania over the weekend and plan to hold a rally in Milwaukee next week, before appearing at the Democratic National Convention in Chicago.

All these events will probably give them further opportunities to stress the issue of drug costs. Biden also frequently touts his measure capping insulin costs for Medicare patients at $35 a month, another program that Harris and Walz are likely to highlight.

Biden, 81, announced late last month that he would not seek reelection to a second term, following a presidential debate with Trump during which he repeatedly stumbled and sometimes had difficulty finishing his sentences.

Biden had been crisscrossing the country to prove that he is up for four more years, but since he stepped aside, he has significantly scaled back his public travel schedule. It remains to be seen how much he will campaign for Harris and how effective a messenger he will be.

The campaign has said that Biden will campaign at some point for Harris in Pennsylvania with Gov. Josh Shapiro, but Biden will not be present on Harris’s bus tour in advance of the convention.

The president will speak at the convention Monday night, and Harris is scheduled to deliver her acceptance speech Thursday, the event’s final night.

Dan Diamond and Meryl Kornfield contributed to this report.