Mr Trump’s predecessor in the White House told a drive-in campaign rally in Philadelphia that Mr Biden and his running mate, Kamala Harris, can mend a fractured country.
He lauded the merits of democracy and citizenship as “human values” that the United States must again embrace.
He said: “America is a good and decent place, but we’ve just seen so much nonsense and noise that sometimes it’s hard to remember.”
Mr Obama’s visit to Philadelphia underscores the significance of Pennsylvania, the Rust Belt state that helped deliver Mr Trump the White House four years ago.
Pennsylvania is the battleground state that Mr Biden has visited the most this campaign season, and Mr Trump has prioritised the state as well, aware that his path to victory would narrow considerably without the state’s 20 electoral votes.
The former president said: “I never thought Donald Trump would embrace my vision or continue my policies, but I did hope for the sake of the country that he might show some interest in taking the job seriously.”
He added that Mr Trump “wants full credit for the economy he inherited and no blame for the pandemic he ignored”.
He disparaged the Republicans’ “shameful” attempts to repeal the 2010 Affordable Care Act while always promising a replacement.
“It’s been ‘coming in two weeks’ for the last 10 years. Where is it? Where is this great plan to replace Obamacare?” he asked. “There is no plan. They’ve never had one.”
