MILWAUKEE -- Donald Trump lashed out Tuesday at former first lady Michelle Obama after she delivered a scathing takedown of his leadership at the Democratic National Convention, while two ex-presidents prepared their own arguments against the White House occupant.
The party is gathering virtually over four days to formally nominate Joe Biden and showcase why their candidate should replace Trump, with Barack Obama's wife offering a stinging criticism of the president as a man lacking the character and skills for the job.
"I thought it was a very divisive speech, extremely divisive," Trump told reporters at the White House.
"Frankly, I would not even be here if it wasn't for Barack Obama," he said. "I would be building buildings someplace and having a good time."
In her pre-taped remarks to the convention -- which has gone almost entirely online because of the coronavirus pandemic -- Michelle Obama urged Americans to rally behind Biden, her husband's former vice president, in the Nov. 3 presidential election.
Biden "will tell the truth, and trust science," she said in a jab at Trump, who has been accused of ignoring the advice of scientists on how to respond to a health crisis which has left more than 171,000 Americans dead and millions without jobs.
"Whenever we look to this White House for some leadership, or consolation, or any semblance of steadiness, what we get instead is chaos, division and a total and utter lack of empathy," she said in unprecedented criticism of a sitting US president by a former first lady.
"Donald Trump is the wrong president for our country," she added. "He is clearly in over his head. He can not meet this moment."
After a night of hard-hitting attacks on Trump from Obama, Vermont Senator Bernie Sanders and others, including several Republicans, the convention is to feature remarks on Tuesday by two former presidents -- Jimmy Carter and Bill Clinton.
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Jill Biden, who has been married to the candidate since 1977 and has campaigned at length for him, is also scheduled to speak. The educator from Pennsylvania will deliver a personal testimonial about why her husband is the best person suited for the Oval Office.
Also on tap is New York Rep. Alexandria Ocasio-Cortez, a rising star in the progressive wing of the party.
The convention on Tuesday also holds its "Roll Call Across America," the formal vote by more than 3,900 delegates from 50 states and seven territories who choose the party's nominee.
Biden clinched that race in early June when he secured the majority 1,991 delegates needed to win the nomination.
The moment has always been a TV-friendly highlight at normal conventions, but this week's organizers have not publicly stated what the delegate vote will look like.
Former president Obama will speak on Wednesday along with 2016 Democratic presidential nominee Hillary Clinton and Biden's running mate, Sen. Kamala Harris of California.
The convention is to culminate on Thursday when the 77-year-old Biden formally accepts the Democratic nomination and delivers his acceptance speech.
US presidential nominating conventions are traditionally raucous events featuring rousing speeches, balloons and confetti and thousands of delegates from around the country.
But the Democratic convention in the Midwestern city of Milwaukee and next week's Republican event in North Carolina have been forced to go almost entirely online because of the COVID-19 outbreak.
Politics professor Larry Sabato at the University of Virginia gave the Democrats' virtual convention a thumbs-up after opening day.
"This show, this longest political TV ad ever, isn't designed for the junkies but for people who dip in for 10 minutes before going back to Netflix," Sabato said. "And that's smart."
Biden leads Trump in the polls and the Republican incumbent has been desperately seeking to persuade Americans that the pandemic is behind them and that the situation is improving.
"My Administration and I built the greatest economy in history, of any country, turned it off, saved millions of lives, and now am building an even greater economy than it was before," Trump tweeted Tuesday.
Trump also continued his attacks on mail-in voting, insisting without proof that it would be "a disaster" for the country.
"It'll end up being a rigged election or they will never come out with an outcome," he said. "They'll have to do it again and nobody wants that. And I don't want that."
Trump has threatened to block extra funding that Democrats say is urgently needed to allow the US Postal Service to process millions of ballots.
While Democrats hold their convention, Trump has been visiting battleground states.
He visited Minnesota and Wisconsin on Monday and heads Tuesday to Iowa and Arizona.