Vice-President Kamala Harris and President Joe Biden have appeared at an event together for the first time since the president ended his run for a second term and Ms Harris replaced him as the Democratic nominee.
The event, held just outside Washington DC, came as Donald Trump spoke at a news conference in New Jersey - his second campaign event in the past two days.
The Democratic event on Thursday celebrated the Biden administration's newly announced deal to cut the cost of 10 common prescription drugs for millions of Americans.
It also offered a glimpse of the pair's dynamic, weeks into a realignment of the party ticket.
The White House said some 2,300 people attended Thursday's rally in Upper Marlboro, Maryland - a Democratic stronghold.
“I have an incredible partner in the progress we made," the president said. "She going to make one hell of a president."
But more than the policy announcement, Mr Biden boosted his vice-president. He brought the crowd to their feet multiple times.
The warm feelings were mutual.
"There's a lot of love in this room for our president," Ms Harris said. "Few leaders in our nation have done more, on so many issues, including to expand access to affordable healthcare, than Joe Biden."
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Thousands stood in line in the summer heat for the chance to see Mr Biden and Ms Harris speak. Social media video showed hundreds still in line as the venue reached capacity.
It's the latest in a series of events Ms Harris has hosted that have drawn large crowds of supporters, marking a noticeable shift in energy in the presidential race.
Ms Harris, however, has largely avoided media questions and has yet to sit down for an interview since becoming her party's candidate.
Her supporters' enthusiasm is showing up in polling data, too. A recent survey from the Cook Political Report suggests Ms Harris is erasing former President Donald Trump's polling leads in Arizona, Michigan, Pennsylvania and Wisconsin.
Vivian Strong waited three hours to get into Thursday's event. She hoped to be part of a historic moment, she told the BBC.
"I feel a sense of urgency to actually ensure she gets elected," she said. "I would hate to have another administration of the other guy."
Before the president and vice-president took the stage, some supporters led the crowd in chants from Howard University - the historically black university Ms Harris attended in Washington DC.
Many supporters of the vice-president donned pink and green, the colours of the Alpha Kappa Alpha Sorority (AKA) to which Ms Harris belonged.
Linda Jones, a Howard alumna and a member of AKA, said their shared identity excites her. But she was also eager to see Mr Biden speak.
"I'm happy for President Biden to get something accomplished that he's worked so hard for," Ms Jones told the BBC, referring to the prescription drug deal.
"He's such a good man and I felt very bad he was leaving with a cloud, so now I feel [this policy] is one more boost for him."
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Meanwhile, Trump, who spoke from his golf resort in Bedminster, lashed out as Ms Harris over the course of his press conference - his second in as many weeks.
He argued that he was "entitled to personal attacks" against Ms Harris, and hit on his main campaign themes, attacking her record on inflation, crime and immigration.
Trump, flanked by common grocery store items with signs showing cost increases in recent years for each, asked: "How can a family afford that?"
Inflation in the US rose at the slowest pace in more than three years last month, marking relief for consumers. Inflation has been a top financial concern for many Americans.
“You don’t have to imagine what a Kamala Harris presidency would be like, because you are living through that nightmare right now,” Trump said.
"I don't have a lot of respect for her. I don't have a lot of respect for her intelligence," he said, adding: "People say, 'Oh be nice'. But they're not nice to me. They want to put me in prison."
Earlier on Thursday, US media reported that the Secret Service would begin using bulletproof glass to protect Trump whenever he is speaking on stage at outdoor campaign events.
The measure it typically done for sitting presidents, but an exception is being made in the wake of the attempted assassination of Trump last month in Pennsylvania.
The Secret Service declined to comment on the reports.
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