Ronald Reagan scribbled a note in 1989 to his successor above an elephant cartoon. The tradition, started perhaps inadvertently, was continued by Joe Biden.

Have thoughts on the presidential transition and what it means for you over the next four years? We want to hear from you.

Presidential historian Douglas Brinkley looks at the considerable, often heroic achievements of Joe Biden, and at the mistakes that may color historians' view of his presidency, as the man Biden warned is a threat to democracy re-enters the White House.