WASHINGTON - Garrulous, gaffe-prone and great at glad-handing, Vice President Joe Biden has become something else to this White House as his boss embarks on a legacy-building second term: essential.
When talks to avert the fiscal cliff were in danger of collapsing, it was Biden to whom Obama turned to get things back on track.
When tragedy struck in Newtown, Connecticut and 20 young lives were ended in a hail of bullets from a maniac's gun, it was again the avuncular vice president who was tasked with drawing up the response.
Biden's star is rising anew and commentators who once sniffed and smiled when he spoke of running for president in 2016 have now been given pause.
At 70, a successful tilt for the White House in three years time is still a long-shot but there is certainly a spring in Joe's step and he is increasingly becoming Obama's go-to-guy in times of crisis.
In one important way, Biden is a perfect foil for the president.
Where Obama has been criticized for remaining aloof from the backroom-dealing of Washington politics, his deputy appears to relish getting his hands dirty, flashing his pearly whites and forging unlikely alliances.
Biden's verbosity has landed him in trouble in the past.
His statement in support of same-sex marriage last May was seen as forcing Obama's hand even before he was ready to make his views known.
A remark during the campaign that the middle class had been "buried" for the past four years was pounced upon by Mitt Romney's team as evidence of the president's failed economic policies.
But when Obama needed him most, after being trounced by Romney in the opening presidential debate, Biden was right on cue.
He was all fire and passion where Obama had been passive and listless, and his fierce defense of the president's record in a combative face-to-face with Romney running mate Paul Ryan set the tone for the ticket's winning comeback.
When Biden accompanied Obama into the White House in 2008, he brought with him a wealth of experience from Capitol Hill and the world stage.
Known as much for his personal warmth as for his memorable public gaffes, Biden had spent 36 years in the Senate, representing the tiny state of Delaware, before Obama made him vice president.
Having once referred to his predecessor Dick Cheney as the most dangerous vice president in US history, Biden maintained his role at the White House should be defined by strict constitutional limits.
He has not been an echo chamber for the president, however. The two differed over Afghanistan at the front end of Obama's first term, with Biden opposing a 30,000-troop "surge" in American boots on the ground.
Biden grew up in an Irish-Catholic family, far from financially privileged, in the town of Scranton, Pennsylvania, and studied at the University of Delaware and the Syracuse University law school.
In the 2008 campaign, his down-to-earth style and appeal to traditional grassroots Democrats gave him an edge in connecting with working-class voters who were initially wary of Obama and his unusual background.
The young Biden moved to Delaware at age 10 when his father relocated in search of employment. Growing up, he was hampered by a stutter so bad he was cruelly nicknamed "Dash."
In adulthood, he developed a natty dress style and dazzling high-definition smile, but as a child in Scranton he sometimes had to walk barefoot as his family struggled to make ends meet.
He was first elected to the Senate in 1972, when he was just 29 years old. Shorty afterwards, he lost his wife and baby daughter in a Yuletide car crash that also left his two young sons badly injured.
Biden took his Senate oath of office at the boys' hospital bedside, then for many years commuted daily to Washington from Delaware so he could be home each night with them and, from 1977, his second wife Jill Biden.
As chairman of the Senate foreign relations committee, Biden met many of the leading actors on the world stage and was an outspoken critic of then-president George W. Bush's foreign policy.
Unlike Obama, Biden was initially in favor of the Iraq invasion in 2003, but he was later critical of how the conflict was handled after Saddam Hussein was toppled.