He defeated the incumbent, Donald Trump, becoming the first candidate to defeat a sitting president since Bill Clinton defeated George H. W. Bush in 1992. Trump refused to concede, insisting the election had been "stolen" from him through "voter fraud", challenging the results in court and promoting numerous conspiracy theories about the voting and vote-counting processes, in an attempt to overturn the election results.[308] Biden's transition was delayed by several weeks as the White House ordered federal agencies not to cooperate.[309] On November 23, General Services Administrator Emily W. Murphy formally recognized Biden as the apparent winner of the 2020 election and authorized the start of a transition process to the Biden administration.[310]
On January 6, 2021, during Congress' electoral vote count, Trump told supporters gathered in front of the White House to march to the Capitol, saying, "We will never give up. We will never concede. It doesn't happen. You don't concede when there's theft involved."[311] Soon after, they attacked the Capitol. During the insurrection at the Capitol, Biden addressed the nation, calling the events "an unprecedented assault unlike anything we've seen in modern times".