UPDATE: That was quick. The two campaigns have apparently agreed to a date of June 27. Debate to be hosted by CNN.
There's a reason I'm quoting the New York Times. See if you can guess! Via the Times:
President Biden is willing to debate former President Donald J. Trump at least twice before the election, and as early as June — but his campaign is rejecting the nonpartisan organization that has managed presidential debates since 1988, according to a letter obtained by The New York Times.