Joe Biden and Kamala Harris made an upbeat show as they held their first joint public event since Ms Harris replaced the president as the Democratic candidate in November's election.
Chants of "thank you Joe!" rang out from the audience at a community college in Maryland, near Washington.
Mr Biden was celebrated as he took credit for a major deal to reduce medicine prices for retirees on social welfare programs.
But the biggest star was Mr Biden's vice president who has united the Democratic Party and surged ahead in the polls against Republican Donald Trump since her abrupt entry into the race.
"She can make one hell of a president," Mr Biden said of his vice president.
The joint appearance came a couple hours before Mr Trump was due to hold a press conference at his golf club in New Jersey.
The former president has struggled to pivot his campaign since Mr Biden dropped out on 21 July, amid Democratic concerns that he lacked the stamina at the age of 81 to do the job.
Until then, Mr Trump was rising steadily in the polls, in large part on his message that Mr Biden was losing his mental acuity - a charge which gained currency following a televised presidential debate in June.
Now Ms Harris, 59, has the growing momentum against 78-year-old Trump.
And Mr Biden appears reenergised, embracing the role of mentor handing off to his protégé.
In his speech, Mr Biden said the Democrats' plan was to "beat the hell out of" Republican opponents and he prompted laughter on pretending not to know Mr Trump's name - "Donald Dump or Donald whatever".
Ms Harris, set to be confirmed as the Democratic nominee at the party convention in Chicago next week, made a display of vice presidential deference, delivering only short remarks and stressing that it has been her honour to serve under the "most extraordinary human being."
"There's a lot of love in this room for our president," she said to cheers.
The drug prices deal will reduce costs for retirees on ten key medicines, including treatments for diabetes, heart failure and blood clots.
The scope and timing of the deal - which the White House says will save older Americans $1.5 billion and the Medicare federal health insurance scheme $6bn in the first year - is a boost for Ms Harris in an election where cost of living is a major issue.
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In a statement, Ms Harris called the negotiations with pharmaceutical companies "historic" and "life changing".
Americans face the highest prescription drug prices in the world, leaving many people to pay partly out of their own pocket, despite already exorbitant insurance premiums.
Tomorrow, Ms Harris will for the first time lay out details of her economic platform.
The United States' first female, Black and South Asian vice president is expected largely to stick to Mr Biden's economic agenda, while trying to differentiate herself, avoiding voter wrath over the post-Covid pandemic surge in inflation.
Axios reported yesterday that Ms Harris wants to "break with Biden on issues on which he's unpopular," with rising prices being top of the list.
While Mr Trump has long polled more strongly on the economy, a recent poll from the Financial Times and University of Michigan found voters trust Ms Harris more on the issue, by 42 to 41%.
Mr Trump, who survived an assassination attempt on 13 July, is now the oldest presidential nominee in US history.
He did not say what would be the topic of his press conference in New Jersey.
In a speech yesterday, he veered from prepared remarks about the economy to repeated personal insults against "crazy person" Harris, "stupid" Biden and calling Ms Harris's running mate Tim Walz a "clown".
