Mr. Biden has said that if he is elected president, he will take a significantly different approach to the virus, moving aggressively to encourage — and possibly mandate — mask wearing and remaining open to imposing restrictions as needed to slow the spread of the virus.
Mr. Biden’s policy advisers have been developing plans that would go into effect as soon as he took office, including ramping up testing, ensuring a steady supply of protective equipment, distributing a vaccine and securing money from Congress for schools and hospitals.
Under normal circumstances — not counting Mr. Trump’s transition in 2016 — Mr. Biden would most likely wait to push those plans forward. Presidents-elect have generally chosen to stay out of the limelight until Inauguration Day, following the general principle that the United States should have one president at a time.
And departing presidents, even of opposite parties, often try to support the efforts of their successors, especially when the country is in the midst of a crisis.
But few people in Washington expect an orderly transition if Mr. Biden wins.
Mr. Trump is not likely to abide by established traditions, and he has made his views about the virus clear during numerous rallies in the final days of the campaign, telling crowds that a vaccine will soon arrive to end the threat from the virus.
“It’s ending anyway, but we have the greatest companies in the world and we’re literally weeks away,” Mr. Trump told supporters in Butler, Pa., on Saturday. “We’ll eradicate more quickly the virus, wipe out the China plague once and for all, and it’s back to work, back to work, which is what we want. You know what we want? We want normal.”
Dr. Koplan said that if Mr. Biden does prevail, he needs to move quickly to establish relationships with governors and to unveil a national strategy for the pandemic.