"I suspect when we get to election night we may say that Joe Biden has a lead on ballots that have been cast already and then it's a question of how numerous president's supporters will turn up on Election Day to try to put him over the top".
"Early voting is already underway in many states".
Biden flew to North Carolina, a battleground where 1.4 million, or 20%, of the state's registered voters had already voted as of Sunday morning.
His pick for vice president, Senator Kamala Harris, canceled in-person events over the weekend as a precaution after an aide tested positive for COVID-19.
With just weeks until Election Day, Trump continues to trail the Democratic nominee in both national polls as well as fundraising.
So far almost 26 million people have cast a ballot in the election, shattering records, according to the US Elections Project, run by the University of Florida.
In Muskegeon, Mich., he attacked Michigan Governor Gretchen Whitmer, a Democrat, blasting state rules to stop the spread of coronavirus, calling her "dishonest", and making light of a right-wing plot uncovered by the Federal Bureau of Investigation to kidnap her.
Host Chris Wallace, who moderated the first debate, pointed to the number of times Trump interrupted Biden during that event, and asked if the president would conduct himself in a similar manner at the second debate, now scheduled for this Thursday. "This is exactly the rhetoric that has put me, my family, and other government officials' lives in danger while we try to save the lives of our fellow Americans", she wrote.
That includes young people.