Joe Biden spent 36 years in the US Senate, twice ran unsuccessfully for president and has served the last four years as Barack Obama's vice-president.
His chatty, off-the-cuff nature led to some memorable gaffes. Obama and Biden won re-election on Tuesday over Republican challengers Mitt Romney and Paul Ryan.
Here are some key facts about Biden.
Biden, 69, grew up in Scranton, Pennsylvania, and Wilmington, Delaware, in a middle-class family. Occasional financial hardships while he was young gave him a good ear for the concerns of blue-collar workers. A football player in high school and at the University of Delaware, he overcame a stutter in his youth by reciting long passages of poetry before a mirror.
He was only 29 when he won a US Senate seat from Delaware in 1972, ousting an incumbent Republican to become the fifth youngest elected senator in US history. His only political experience at the time was two years on a county council. - A few weeks after the election, Biden's life was shattered when his wife, Neilia, and their three children were in a car wreck while shopping for a Christmas tree. Neilia and their year-old daughter were killed and their two sons were injured. The tragedy left Biden suicidal but he chose to go ahead with plans to serve in the Senate.
Five years later he married Jill Jacobs, who he met on a blind date; they have one child. - After his first wife's death, Biden chose not to move to Washington but instead made a 2 1/2-hour daily round-trip train commute from Delaware to his Senate job so he could spend more time with his sons. Biden said he made the trip more than 7,000 times and in 2011 the Amtrak station in Wilmington was renamed after him.
While on the campaign trail in October, Biden made a reference to Americans having a chance to vote for him for president in 2016. It was unclear if he was serious and his campaign officials would not comment on the remark.
His performance in his October 2012 vice-presidential debate with Paul Ryan was notable for the way he smiled, chuckled and sometimes interrupted while the Republican nominee was speaking.
He is known for his friendly but blunt and loquacious manner, which sometimes leads to embarrassing gaffes and contrasts with President Barack Obama's cautious manner. Biden was caught using the F-word on a live microphone during a White House ceremony with Obama and upstaged the president in 2012 by endorsing same-sex marriage before Obama did so.
Biden has been troubled by two incidents involving plagiarism. In law school he was accused of plagiarising a law review article, which he said was due to a mistaken citation. While running for the Democratic presidential nomination in 1987 he lifted parts of a speech by a British politician without attribution. Backlash from that incident led Biden to drop out of the presidential race the next month.
Biden ran for president in 2008 and dropped out of the race early in the year - but not before making a verbal misstep involving his future boss. His description of Obama as "the first mainstream African-American who is articulate and bright and clean and a nice-looking guy" seemed to some to be condescending, with possible racial undertones.
Biden was on the Foreign Relations Committee for his entire Senate tenure, sometimes serving as its chairman. He focused on Soviet relations, arms control, the Balkans and NATO expansion.
He voted for the invasion of Iraq during the George W. Bush administration but later said he regretted it and spoke against the war. - From being a rival in the nomination stakes, Biden has avoided the curse of vice presidential insignificance and become a close aide to Obama. He often takes the role of contrarian within the administration to ensure all views are being considered and spoke out against the US special forces raid that killed Osama bin Laden in 2011 as being too risky.
Biden is the first Roman Catholic vice-president in US history and his pro-choice position differs from the Vatican's abortion stand. Because of that, he came under fire from the bishop of his Wilmington diocese.