When Barack Obama enlisted Joe Biden as his running mate in 2008, even some of his own campaign aides were skeptical of the wisdom of picking an old-school Democrat known for always speaking his mind - and sometimes getting tripped up by his words.
Four years later, after leaving a trail of memorable "Bidenisms" across the Internet, the white-haired former U.S. senator is now heading for a second term as vice president, his status secure as Obama's trusted, all-purpose No. 2.
With Obama's re-election victory, Biden will not only remain in a job often described as being a heartbeat away from the presidency but will see his name automatically in play as a potential 2016 contender for the White House.
Whether he decides to run - and, in fact, has any realistic chance of winning - remains to be seen, especially given questions about his age and temperament. He is 69, famously prone to rhetorical gaffes and could face a formidable Democratic rival if Hillary Clinton again sets her sights on the presidency.
But Biden's political future will no doubt depend to a large extent on what happens in a second Obama term and what role he carves out for himself.
Biden, who has established himself as congressional envoy, foreign policy troubleshooter and popular ambassador to the working class for Obama, is likely to be assigned to help navigate some of the administration's biggest challenges.
That could include tapping his congressional contacts to help avoid the looming "fiscal cliff," coordinating strategy for the U.S. withdrawal from Afghanistan and even working to keep Israel from blindsiding the United States with an attack on Iran's nuclear sites.
"It will be whatever is the highest and best use of him," said Ted Kaufman, Biden's longtime chief of staff before being appointed to serve out his term as Delaware's senator.
FOLLOWING FIRST-TERM MODEL
The formula for Biden's role in a second term may have already been laid out in the first. Obama turned to him early with assignments that fit the very reasons he was chosen as running mate - his 36-year Senate career, deep foreign policy experience and backslapping political persona.
Biden notably succeeded in avoiding the vice presidential curse of irrelevance and won the president's ear.
Once skeptical Obama aides came to regard him as a consummate team player - in stark contrast to the power-hoarding vice presidency of his predecessor, Dick Cheney, who served two terms under Republican George W. Bush.
That did not mean things always went smoothly for Biden.
He was tasked with overseeing $787 billion in stimulus funds, a program credited by economists with averting a deeper recession but which polls showed most Americans viewed as wasteful spending.
He was later called on to try to resolve disputes with Republicans, but was unable to broker compromise on deficits in 2011 - and may fare little better with a still-divided Congress.
Biden, former chairman of the Senate Foreign Relations Committee, also served as Obama's point man on Iraq, helping fulfill his promise to withdraw U.S. forces. But he failed to secure a deal to maintain a modest troop presence there.
Obama also gave the go-ahead for the raid that killed Osama bin Laden despite Biden's warning that it was too risky.
It was on the campaign trail, however, where Biden may have served Obama best, using his working-class roots to connect with voters in a way that his younger, less-effusive boss could not.
It was Biden who lifted Democrats' hopes with a forceful debate performance against Paul Ryan after Obama did poorly against Mitt Romney in their first encounter.
But Biden's irrepressible, off-the-cuff style has also gotten him in trouble. Last month, he told a rally that the middle class had been "buried the last four years," essentially Obama's time in office.
Biden also created a stir at the White House signing ceremony for Obama's healthcare bill in 2010, when the microphone caught him saying, "This is a big fucking deal."
He committed another lapse in May when he told a talk show he was "absolutely comfortable" with gay marriage, forcing Obama to move up his own plans to pronounce a changed position.
The White House insists the focus on Biden's unscripted moments is overdone and that Obama values his advice. But misstatements gave ammunition to the Romney campaign and fueled speculation right up to this summer's Democratic convention that he might be dumped from the ticket in favor of Hillary Clinton.
Now, the Washington guessing game will be whether Biden, like many vice presidents before him, will seek the only higher office. He made two runs for the White House. The first was the 1988 campaign, which he exited because of a plagiarism scandal, and the second was against Obama in 2008 when his bid drew little support
Biden has not ruled anything out. But he joked about his future on a visit to Florida late last month. Trying to convince a man of the benefits of healthcare reform, he said, "When your insurance rates go down, then you'll vote for me in 2016."
He fueled further speculation after casting his ballot on Tuesday. When asked if it would be the last time he would vote for himself, he said with a grin, "No, I don't think so."
Still, one Biden confidant sees any decision far off.
"I'm going to suggest after the election is over that he look into 2016. But there are five million questions," Kaufman told Reuters on Friday. "We don't talk about it. I was on a plane with him for three days, not a word."
Age would be a consideration. Biden would be just shy of 74 on Election Day 2016, which would make him the oldest president ever sworn into office if he won.
But some critics suggest Biden's rhetorical excess raises questions about his fitness for the job. "He doesn't really have the reputation as presidential material anymore," said John Petrocik, a political scientist at the University of Missouri at Columbia, who has studied the vice presidency.