How Joe Biden Works

Biden sat out the 2016 presidential race, explaining that he was still too upset over Beau's death to give his full energy to a presidential campaign. But after Donald Trump took office, Biden became a vocal critic of Trump administration policies that actively dismantled the Obama administration's work on issues like immigration, health care and the environment. Biden later said he was also deeply disturbed by President Trump's response to the 2017 clashes in Charlottesville, Virginia, sparked by a white supremacist rally [source: Biography].

As Biden edged closer to announcing a White House run in 2019, allegations emerged that he had acted inappropriately around female staffers and colleagues, including accusations that he had kissed one woman on the back of the head and sexually assaulted another woman in a Senate hallway in 1993 [source: Relman and Sheth]. Biden addressed the accusations, but came short of apologizing.

Another concern was Biden's age. If elected, Biden would enter the White House at 78 years old, making him the oldest president to hold office. And with Biden's history of aneurysms, his health was a legitimate concern. Biden's cause was probably helped by the fact that his main challenger during the primaries, Bernie Sanders, was also in his 70s and had his own significant health problems.

Despite the rocky start, Biden still led in early polls of potential challengers to President Trump, prompting the former vice president to officially announce his 2020 candidacy in April 2019 [source: Biography].

Things took an unexpected turn in September 2019 when an intelligence department whistleblower claimed that President Trump had abused his power to pressure the Ukrainian government to investigate both Biden and his son, Hunter. Trump claimed that Hunter had committed fraud as a board member at Burisma Holdings, a Ukrainian energy company, and that Biden had used his influence as vice president to quash a Ukrainian investigation [source: Bruggeman and Tatum]. The Ukraine controversy ultimately led to President Trump's impeachment by the House of Representatives and ultimate acquittal by the Senate.

Biden registered poor showings in early Democratic primaries, but was still largely seen as the man to beat. In televised debates, more liberal candidates attacked his record on the 1994 crime bill and his failure to support busing to racially integrate public schools in the 1970s [source: Biography]. The turning point came when Biden won the South Carolina primary in convincing fashion, solidifying his position with Black voters, a key constituency if Democrats hoped to beat President Trump in 2020.

In short order, Biden's top Democratic rivals — Elizabeth Warren and Bernie Sanders — dropped out of the race in March and April 2020, clearing the path for Biden to become the 2020 Democratic nominee.