One of the most recognizable names in U.S. politics, Biden served for two terms as Barack Obama's vice president after nearly four decades as a senator from Delaware. His high-profile, working-class background and connection to the Obama years would help him enter the race as a front-runner, though he faces questions about his age and whether his more moderate record fits with a party that has become more liberal.
With a record in elected office that stretches half a century, Biden faces multiple challenges.
Last month he struggled to respond to a complaint from Lucy Flores, a 2014 lieutenant governor nominee in Nevada, that he made her uncomfortable by touching her shoulders and kissing the back of her head before a campaign event. A few other women have made similar claims, though none has alleged sexual misconduct.
The incident is just a taste of the harsh vetting from both Democrats and Republicans expected for Biden, who has run for president twice before but never from such a strong political starting point.
His first White House bid in 1988 ended after a plagiarism scandal. And in recent weeks, he was repeatedly forced to explain his 1991 decision, as Senate Judiciary Committee chairman, to allow Anita Hill to face questions about her allegations of sexual harassment against Clarence Thomas, then a nominee for the Supreme Court.
Biden has since apologized for his role in the hearing. But in the #MeToo era, it's another example of why critics believe he may struggle to catch on with the Democratic primary voters of 2020.
On paper, however, he may be well positioned to take on Trump in a general election.
The Republican president's allies have privately warned that Biden might be the biggest threat to Trump's reelection given Biden's potential appeal among the white-working class in the Midwest, the same region that helped Trump win the presidency.
*The Associated Press has contributed to this report.