Trump, who has been holding more campaign events in battleground states amid rising coronavirus cases, voted for himself on Saturday at a public library across the street from one of his golf clubs in the battleground state of Florida. He changed his residency from New York a year ago.
The number of people who have voted early represents more than 53 per cent of the total turnout in the 2016 election, according to data compiled by the US Elections Project at the University of Florida.
Delaware allows some early voting by appointment.
Biden holds a comfortable lead in national polls, which also show a public increasingly dismayed by Trump's handling of the largest public health crisis in US living memory. Polls in battleground states that might decide the election are tighter.