Washington (CNN) Joe Biden knows more than most anyone about the nuts-and-bolts of running for president. What he knows less about is how to win.

As the former vice president nears a decision about entering the Democratic presidential race, his two failed bids for the White House remain a stinging reminder of a critical question confronting a potential candidacy: Can he win the big one?

While Biden is now celebrated by many Democrats as a beloved statesman after back-to-back victories with President Barack Obama, he has been far less successful carving his own path to the Oval Office. He not only lost his two previous races in 1988 and 2008, he fell profoundly short, with both campaigns highlighting some of his shortcomings.

Those defeats, spanning two decades of his time in the Senate, are bubbling just beneath the surface in discussions of Biden mounting a third bid for the presidency. He and his advisers insist those political wounds would ultimately make him a stronger candidate if he decides to take the step of trying to unseat President Donald Trump.

"I am a gaffe machine, but my God what a wonderful thing compared to a guy who can't tell the truth," Biden told an audience late last year. "I'm ready to litigate all those things. The question is what kind of nation are we becoming? What are we going to do? Who are we?"

Should Biden decide to join the ever-growing field of 2020 Democratic hopefuls, he would start in an unfamiliar place: as a front-runner. But even many admirers concede he's a front-runner in name only, with his advantage in early polls attributed to his high name recognition and his recent tenure as vice president.

The pole position could also be a curse, particularly in a party that famously loves to fall for a fresh face over a candidate with the longest resume.

Yet for all of those challenges, conversations with more than two dozen aides, donors and supporters, point to a consensus that Biden is still likely to run in what he repeatedly calls the most important presidential race of his lifetime. But until he gives the final nod, many caution he could also decide against it.

"His thinking is centered around one thought: There has to be a new president," a top Democrat close to Biden said. "That's what his campaign would be about."

Another ally who recently spoke to Biden said he was left the impression that the former vice president was closer to launching a bid than retreating to the sidelines. And his team is preparing a detailed campaign plan to be ready the moment he pulls the trigger, several people familiar with the matter say.

"It was clear to me that he is at a point where he is certainly much more likely to announce a candidacy than announce he's not running -- although he did not give me that final decision," the ally said, speaking on condition of anonymity to discuss a private conversation.

Biden is aware that the moment he reveals his intention to run, this ally said, he would "immediately become the target of not only the sitting president, but he'll in essence become the target of every other Democrat."

While he's reaching out to some close supporters, Biden has not had any recent, substantive discussions about his plans with Obama, two people familiar with the matter say. The former president plans to stay neutral in the race, although a Biden candidacy could complicate those intentions.

For Biden, one question that remains unresolved for he and his wife, Jill, is the unease some family members have about his potential candidacy. The family is still dealing with the aftermath of the 2015 death of their son, Beau, which is among the leading reasons Biden stepped away from running in 2016.

At his book tour event in Vermont last month, Biden said he wanted to honor a promise he made to his son to stay engaged in public life after his death, but he also said, "I want to spend as much time as I can with my family. I have five grandchildren who adore me."

"Beginning, middle and end is family," he added.

The family's complicated dynamic was underscored Friday in a Vanity Fair story that raised concerns about whether Biden's son Hunter's divorce and work would play a role in a potential campaign. Hunter Biden and his wife divorced in 2017 and the younger Biden son confirmed he had begun a romantic relationship with his brother Beau's widow.

In a statement to Vanity Fair, Hunter Biden said his "complicated divorce ... and equally complicated life" would not stop his father from running for president, if that's what his father wants to do.

"Our journey as a family—yes, including my own difficulties with my marriage—have made us unbreakable. It isn't, of course, that we don't suffer. We do. The point is that we don't give up, no matter how much we suffer," Hunter Biden told Vanity Fair.

"So, you ask me, whether my father might not run for President because of reports about me in the news. What you fail to realize, in asking such a question, is that my father has always been proud of me—whether when I was volunteering for the Jesuits, or working as a lawyer. And he remains proud of me today. He loves me. And he loves the American people far too much to let any form of adversity stand in the way of service."

But several people close to the family say they believe Biden's determination to make Trump a one-term president could outweigh any family uncertainty.

"He's running unless he hears a reason not to," another Biden loyalist said. "The approach has been to function as though he's going to say yes."

Should he run, how Biden withstands the early political criticism -- and later navigates the ideological winds blowing inside the Democratic Party -- will play a large role in determining the staying power of any potential candidacy.

Not only would Biden be faced with defending the record of the Obama administration -- particularly foreign policy decisions like deportations and Syria -- his Senate career of nearly four decades will also come under the microscope.

His handling of Anita Hill's testimony during Clarence Thomas' 1991 Supreme court confirmation, ties to the financial services industry, which has a strong base in his home state of Delaware, championing of the 1994 crime bill and even his penchant for gaffes would all be fair game for challengers.

If he enters the race, Biden, 76, will be among the oldest candidates in the primary field at a time when some in the Democratic Party are calling for younger and more diverse leaders.

Yet several Biden loyalists believe the desire to defeat Trump would take priority over any questions surrounding his candidacy.

"I think he'll have all his ducks in a row before he pulls a trigger on anything," said Dick Harpootlian, a South Carolina state senator and longtime friend and donor to Biden. "I think if he runs, he'll be clearly the early on and the consistent favorite."

The contours of the race are quickly developing with several potential rivals already in the race or close to joining, including Sens. Elizabeth Warren of Massachusetts, Kirsten Gillibrand of New York and Kamala Harris of California. And a draft movement is gaining attention for Beto O'Rourke, a former Texas congressman.

But several friends and supporters of Biden argue his decades of experience, which includes 36 years in the Senate and two terms as vice president, give him a tremendous advantage over other Democrats eyeing the White House.

"I think Joe has the ability to do some things that other candidates don't," said Alabama Sen. Doug Jones, a friend of Biden, citing his strength appealing to blue collar workers. "I think Joe's strength in the African American community and the Democratic base is very, very strong and much stronger than what people may give him credit for."

As they await Biden's decision, members of his inner circle have quietly worked to lay preliminary groundwork for a possible campaign, even without having the explicit assurance he will run. They've fielded calls and e-mails from interested staffers, held early conversations about campaign structure and reached out to donors. But there's only so much the team can do before getting the official go-ahead for a run from Biden.

"The pieces are in place," a Democratic adviser familiar with the conversations said. "People are ready to go. They're just waiting for him."

Greg Schultz, the executive director of Biden's American Possibilities PAC, has sought advice from Democratic operatives, supporters and strategists in key early states like Iowa and South Carolina, according to people familiar with the conversations.

Shortly before the holidays, Schultz and two other top Biden advisors, Mike Donilon and Steve Ricchetti, huddled with Louisiana Rep. Cedric Richmond, the former chair of the Congressional Black Caucus, at a restaurant near the Capitol. It's one of several meetings top Biden aides have had with party leaders.

While some donors have also been growing impatient, eager to choose another candidate if Biden doesn't run, he is likely to have a far easier time raising money than most other candidates, at least among top donors.

"There's no one in politics who's built better and long-lasting national relationships than the vice president," said Rufus Gifford, the finance director for the Obama-Biden re-election campaign. "There's real loyalty amongst the Democratic Party finance base, institutional donors and Obama world. There's a lot of loyalty. There's a lot of support."

As Biden's decision comes into sharper focus, he has kept a relatively low profile this year, splitting his time between Delaware and Washington. Over the past two weeks, he's held several meetings, including with freshmen lawmakers he endorsed like Rep. Joe Neguse of Colorado, and his only public comments have come in the form of a few tweets.

But he is about to step up his public appearances over the next two weeks, including a Martin Luther King Jr. breakfast in Washington on Monday as well as trips to Texas and Florida.

A week ago, Biden was spotted at a Delaware running store. Another shopper, Michael Withrow, watched Biden try on new running shoes and test them on a treadmill. Biden told others at the store that he's been "lifting and getting back into running."

Withrow later told CNN he thought about asking Biden, "'Is that the only running you're doing?'" He added, "But I didn't."