Biden announced in early August that Sen. Kamala Harris, D-Calif., would join him on the Democratic ticket as his vice presidential nominee, after pledging to choose a woman for the role in March. Harris was long considered to be a front-runner in the search, despite a testy debate stage exchange with Biden over busing when they were competing for the Democratic nomination for president. Biden credited his late son's close relationship with the senator in helping him make his decision.
Name: Joseph Robinette Biden Jr.
Date of birth: Nov. 20, 1942
Hometown: Scranton, Pennsylvania
Family: Married to Jill Biden, father to Hunter, Ashley and the late Joseph Robinette 'Beau' III and Naomi. Biden's first wife, Neilia, died in a car accident with their baby daughter Naomi in 1972. Beau Biden died in May 2015 of brain cancer.
Education: He graduated from the University of Delaware and Syracuse Law School.
What he used to do: He served as vice president from 2009 to 2017. From 1973 to 2009, Biden served in the U.S. Senate and was on two key committees as both ranking member and chairman: the Senate Foreign Relations Committee and the Senate Judiciary Committee. He also served on the New Castle County Council after finishing law school. Since leaving the White House, Biden and his wife launched the Biden Cancer Initiative to invest in efforts for cancer prevention, detection, diagnosis, research and care.
Key life/career moments:
After publicly supporting same-sex marriage ahead of his boss, Biden reportedly apologized to Obama in 2012. But Obama said in an interview with ABC's “Good Morning America” co-anchor Robin Roberts, "I think Joe is an extremely generous loving person. And I think he was responding honestly in terms of how he felt."
Perhaps one of the most poignant moments of his vice presidency came when Obama surprised Biden with a Presidential Medal of Freedom.
The University of Pennsylvania announced the Penn Biden Center for Diplomacy and Global Engagement to honor his "unsurpassed understanding of diplomacy and far-ranging grasp of world issues" in 2017. That same year, the University of Delaware announced a partnership with Biden to launch the Biden Domestic Policy Institute.
During Biden's Senate career, he oversaw the confirmation of Supreme Court Justice Clarence Thomas in his role as the head of the Judiciary Committee. He was criticized for his handling of the hearing after Anita Hill testified before the committee, and his failure to defend Hill as she faced questioning from an all-white, male committee, as Republican members sought to discredit her testimony.
Biden voted against Thomas, but the Senate nonetheless confirmed the then-nominee. Biden has publicly apologized to Hill, and said in March at the Biden Courage Awards he regrets he "couldn't come up with a way to get (Hill) the kind of hearing she deserved."
Biden has also led the charge on the sweeping, bipartisan 1994 crime bill -- a bill Biden referred to as the "Biden Crime Bill" during his 2008 presidential campaign -- which critics say had a disproportionate impact on minority communities, particularly due to mass incarceration.
Biden undertook three presidential runs during his nearly 50 years in public life, with the first, in 1987, ending before any primary voting took place due to a plagiarism scandal. In that case, Biden quoted British Labor party leader Neil Kinnock without attribution. Biden also faced questions of plagiarism in law school after a paper he wrote did not include proper citation for some of the text.
He admitted to that in 1987, called it a "mistake" and said that there wasn't "malevolent" intent, according to reports at the time.
His second presidential run during the 2008 primary ended after the Iowa Caucuses, where Biden received less than 1% of the vote.
Where he stands on some of the issues:
Biden has expanded his plan for higher education and proposes offering free college tuition for public universities, historically black colleges and universities, and minority-serving institutions to families making less than $125,000, along with his previous pledge to make community college tuition free.
Biden's plan for health care would attempt to make the Affordable Care Act easier to navigate with more choices. His plan would expand upon the Affordable Care Act passed under the Obama-Biden administration and provide a public option for patients to buy into, rather than Sen. Bernie Sanders' "Medicare for All" system that several of Biden's rivals advocated for during the primaries.
Biden has also put a large focus on addressing climate change, calling it one of the four crises facing the country today. This summer, he unveiled a sweeping new proposal that called for the United States to achieve a carbon-free power sector by 2035 and a $2 trillion investment over his first four years in office in green energy and infrastructure to combat the threat of climate change.
Biden has also put forth several plans to address the coronavirus pandemic, pledging to follow the science and heed the advice of experts. Biden has said he would advocate for a nationwide mask mandate in order to contain the virus and help the economy rebound, and he has also advocated for a safe and effective vaccine free of political pressure. According to one adviser, the former vice president is working through "multiple scenarios" on how to deal with the virus if elected.
In the wake of protests across the country over racial inequality, Biden has not joined the calls to defund police departments, but he advocates for providing an additional $300 million in funding for community-based policing, as well as pairing police with mental health experts to be able to better address community needs, while also advocating for a national use-of-force standard.
The Biden campaign shifted toward the 2020 general election earlier this year with a fundraising gap that seemed like a world away from the Trump campaign. Entering April, and before he became the party’s nominee, the Biden campaign was more than $180 million behind the president's reelection campaign in cash on hand.
Fast forward five months, Biden has managed to eliminate that fundraising gap, entering the month of September with $140 million more on hand than Trump. The former vice president in recent months has repeatedly outraised the president, and during the month of August, Team Biden completely outpaced Trump's team, raking in $364 million compared to Trump's $210 million. According to the campaign, 57%, or more than $205 million of Biden's August haul came from small-dollar donations online.
Biden's record-level fundraising success in August came at the same time as he picked Sen. Kamala Harris as his running mate. The California senator, who raised roughly $40 million by the time she dropped out of the presidential bid in December, has been a major boost for Biden's fundraising efforts, courting big-dollar donors at fundraisers as well as small-dollar donors online.
What you might not know about him:
As a child and teenager, he struggled with a stutter. A young Biden overcame the affliction through public speaking.
During his college years at the University of Delaware, Biden played football.
Biden was first sent to Washington in 1972 when the people of Delaware elected him to the U.S. Senate at 29 years old. He was one of the youngest people elected to a seat in the upper chamber.
In the weeks after being elected to the Senate in 1972, tragedy struck the Biden family after a car accident killed his first wife, Neilia and their 1-year-old daughter, Naomi, and severely injured his sons, Beau and Hunter. In 1977, he married Jill Biden.
After Biden's 46-year old son, Beau, died of brain cancer in 2015, Obama eulogized the former Delaware attorney general during a memorial service. The Biden family received 72,000 condolences through the White House's virtual system after the death of Beau -- and condolences were submitted from every state, according to the vice president's office.
One of Biden's significant achievements during his time at the helm of the Judiciary Committee was appointing California Sen. Dianne Feinstein to the dais. She was the first woman on the committee.
ABC News' Soorin Kim, Sruthi Palaniappan and Christine Szabo contributed to this report.