The tradition in Presidential elections is for the loser to concede with grace and statesmanship.
One can forget about that with President Donald Trump, who is promoting conspiracy theories, and according to some sources, has every intention of refusing to cooperate on the transition, and staying in the White House on Inauguration Day, January 20, 2021, refusing to leave the building or attend the inauguration of his successor.
Other Presidents have refused to attend the inauguration of their successor, including John Adams when Thomas Jefferson was inaugurated in 1801; John Quincy Adams when Andrew Jackson was inaugurated in 1829; and Andrew Johnson when Ulysses S. Grant was inaugurated in 1869.
We have seen in modern times all of the Presidential losers concede graciously—Richard Nixon in 1960, Barry Goldwater in 1964, Hubert Humphrey in 1968, George McGovern in 1972, Gerald Ford in 1976, Jimmy Carter in 1980, Walter Mondale in 1984, Michael Dukakis in 1988, George H. W. Bush in 1992, Bob Dole in 1996, Al Gore in 2000, John Kerry in 2004, John McCain in 2008, Mitt Romney in 2012, and Hillary Clinton in 2016.
Donald Trump is acting like a spoiled child, a privileged character, a prima donna, who clearly would love to be an authoritarian dictator and has been a threat for four years, but the American people have clearly made him aware that his “employment” in the White House for four more years is not desired, and that he has, effectively, been “fired” by a vast margin of about 5-6 million popular votes by the time all of the votes are counted!