WASHINGTON - Former vice-president Joe Biden often talks about the black hole, that depthless void in a grieving mourner's chest that threatens to consume him whole.
He knows all about that despair. Mr Biden is a man shaped by tragedy and profound loss: the deaths of his first wife Neilia and baby daughter Naomi in a car accident in 1972, and the death of his elder son Beau, who had brain cancer, in 2015.
The elder statesman has turned this familiarity with grief into a cornerstone of his candidacy.
In his third and best shot at the US presidency, Mr Biden has positioned himself as a healer of the nation's divides who can empathise with the pain of racial justice protesters and the heartbreak of the 200,000 families who have lost loved ones to the ongoing Covid-19 pandemic.
Yet the avuncular 77-year-old politician, well-known for his folksy charm and blunt comments, is far from infallible after nearly five decades in politics.
Born in Scranton, Pennsylvania, in 1942, Joseph Robinette Biden Jr - who was given his grandmother's maiden name for a middle name - moved with his family to Delaware at the age of 10 after his father found work there.
Money was occasionally tight enough at home that he once had to use a pair of nuts and bolts as cufflinks.
The younger Biden worked hard to beat a stutter for which classmates picked on him. He graduated in 1965 with a Bachelor's degree in history and political science at the University of Delaware in Newark, and went on to get his law degree from Syracuse University, where his sweetheart Neilia Hunter was studying. They married in 1966, and went on to have three children: Beau, Hunter and Naomi.
In 1972, then 29-year-old Mr Biden unseated Delaware's incumbent Republican senator, becoming the sixth-youngest senator in US history.
But weeks later, while he was in Washington DC hiring staff, his wife and Naomi died in a car accident. "I could not speak, only felt this hollow core grow in my chest, like I was going to be sucked inside a black hole," Mr Biden wrote in his 2007 memoir, Promises To Keep.
It was Jill Jacobs who gave him his life back and made him start to feel normal again, Mr Biden wrote of his second wife, whom he met on a blind date and married in 1977. They had a daughter, Ashley, four years later.
Long public service
A "middle of the road" Democrat, as he called himself, Mr Biden was a long-time member and eventual chairman of both the Senate committees on foreign affairs and the judiciary.
He has called the 1994 Violence Against Women Act, which took aim at domestic violence and sexual assault, his proudest legislative accomplishment.
But his past positions on criminal justice, desegregation and Supreme Court confirmation hearings have also been criticised by Democrats now.
He admitted last year that he had not always been right on criminal justice issues, calling tougher sentences on drug possession a "big mistake".
Mr Biden mounted a bid for the presidency in 1987, but later withdrew after a plagiarism scandal in which he did not properly credit a British lawmaker for lines in a speech.
He suffered two brain aneurysms a few months later, from which he took seven months to recuperate.
Mr Biden ran unsuccessfully for the Democratic nomination for President in 2008, but accepted when then-Senator Barack Obama asked him to be his running mate.
As President Obama's vice-president from 2009 to 2016, Mr Biden helped steer America through the recession, overseeing infrastructure spending in the stimulus package and working with Democrats and Republicans to avert a federal government shutdown in 2011.
He also had a hand in foreign policy, particularly when it came to Russia, Libya and Iraq.
Mr Biden has remained close to his family, who rallied to support the seriously ill Beau, now an attorney general of Delaware.
"He had the best of me, but with the bugs and flaws engineered out," Mr Biden wrote proudly of his elder son, who died in 2015 after a two-year battle with brain cancer.
"May 30. 7:51pm. It happened, I recorded in my diary. My God, my boy. My beautiful boy," Mr Biden wrote in Promise Me, Dad, his 2017 memoir.
Again the black hole opened up. Mr Biden later said it was his promise to Beau "to be okay" that kept him going, though he ultimately decided not to run for president in 2016.
What drew him back to politics and prompted him to run for the White House was President Donald Trump's failure to denounce white supremacists at a rally in Charlottesville, said Mr Biden. The former vice-president has repeatedly called the presidential contest "a battle for the soul of this nation".
Mr Biden, who acknowledges his "reputation as a gaffe machine", is still prone to slip-ups and politically incorrect comments. He has been told off for being inappropriately touchy-feely with women supporters, and has denied an allegation of sexual assault in 1993 by his former staff assistant Tara Reade, which media reports note was inconsistent with a complaint she filed that year.
He still loses his cool at times, particularly over accusations against Hunter, whom he refers to as "my only surviving son".
Said Biden biographer Evan Osnos in a National Public Radio interview: "If you talk to the 77-year-old Joe Biden now, he's a man who is at peace.
"He's at peace from a series of hard-won scars."
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