Trump and Biden address ballots and voting integrity.

“As far as the ballots are concerned, it's a disaster,” said President Donald Trump as millions of ballots are expected to be mailed out.

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Biden becomes 46th president of US in historic inauguration.

Biden becomes 46th president of US in historic inauguration.

Joe Biden was sworn in minutes after Kamala Harris became the first female, Black and South Asian vice president in a ceremony marked by messages of hope and healing and star performances.

Presidential historian: 'We’ve rarely seen America so fractured'.

Presidential historian: 'We’ve rarely seen America so fractured'.

Historian Mark Updegrove speaks about the importance of seeing outgoing and incoming presidents together on Inauguration Day and the challenge of uniting the country.

President Biden signs flurry of executive orders on 1st day.

President Biden signs flurry of executive orders on 1st day.

On his first day, President Joe Biden signed multiple executive orders, including rejoining the Paris Climate agreement, and reversing former President Donald Trump’s travel ban.

By the Numbers: Highlights of historic Inauguration Day.

By the Numbers: Highlights of historic Inauguration Day.

A look at how the inauguration of President Joe Biden and Vice President Kamala Harris unfolded in a day of firsts. ABC News Live Prime, Weekdays at 7EST & 9EST WATCH the ABC News Live Stream Here: SUBSCRIBE to ABC NEWS: Watch More on LIKE ABC New...

President Joe Biden’s star-studded inaugural night

President Joe Biden’s star-studded inaugural night

From Katy Perry to Lin-Manuel Miranda, stars and Americans around the country join President Joe BIden’s message of unity on inauguration night. ABC News Live Prime, Weekdays at 7EST & 9EST WATCH the ABC News Live Stream Here: SUBSCRIBE to ABC NEW...