With a burgeoning field of Democratic candidates, former vice president Joe Biden, pictured in December, is still on the fence about whether he will run for president. (Rick Bowmer/AP)

Joe Biden was going to decide whether to run for president by the end of 2018. That deadline slipped. Just after New Year’s he said he would decide “soon.” Mid-January came and went with no decision. By the end of January?

“We’ll make the decision soon,” he said at the time.

Now into mid-February, with a burgeoning field of Democratic candidates, Biden is still on the fence, neither in nor out, in a lingering state of political limbo. Some potential staffers have already defected, and some of his supporters worry the prolonged indecision could begin to threaten his chances.

If former Democratic congressman Beto O’Rourke, another on-the-fence candidate, has had a public quest — Instagram-living and Medium-posting his way toward a presidential run — then Biden has been quietly agonizing, with a decision-making process that has been lengthier, yet utterly familiar.

Perhaps more than any other politician in American history, Biden has had a near-quadrennial regimen of mulling whether he can, should or will run for president. Over nearly four decades — from the time he was a young senator until now, as a septuagenarian former vice president — he has engaged in a process of prolonged angst about whether to run. Or not to run.

It’s become a well-practiced process — one that includes long discussions with family over Thanksgiving in Nantucket, Mass., debates with advisers in the living room of his home in Delaware — but not one that has gotten smoother over time, nor led to successful campaigns.

The Washington Post spoke with more than half a dozen of Biden’s close confidants and people familiar with his thinking. Many would agree to speak only on the condition of anonymity until he makes a decision.

Staff members who have committed to work for him if he runs have stopped guessing on a decision date. On a few occasions, some members of his inner circle were convinced he was ready to pull the trigger, only to find it did not happen. Year-end family discussions about a potential run did not end the process, which people around Biden describe as intensely personal for the former vice president.

“This isn’t just treading water, but I don’t know how close we are to the shore,” said a person familiar with the planning process who spoke on the condition of anonymity to discuss internal deliberations.

As Biden has deliberated, other campaign professionals who had previously expressed interest in joining his effort have decided they can no longer wait. The circle of senior advisers who have been drafting his campaign plan and conducting interviews with potential staff members have repeatedly had to add names to their internal hiring lists, as their candidates have signed on to other campaigns, according to a person familiar with the planning.

One person in line to become a state director for Biden in South Carolina recently signed with a rival, said another person involved in the planning. Other presidential candidates have aggressive travel and staff-hunting scheduled in the state.

“This has got to hurry up,” said a person familiar with conversations that the Biden team is having in South Carolina. “He is running out of time.”

Advisers still say there is plenty of talent available to staff the campaign should Biden run, and a core crew of senior campaign consultants has decided to stay on the sidelines until Biden makes a decision. Multiple people involved in the effort said the planning process has not slowed in recent weeks, with Biden’s top advisers making more calls and holding more detailed discussions in early primary states like South Carolina about what a campaign apparatus would look like.

Biden, too, will be more visible in coming weeks. On Saturday, in Munich, he began a series of four February speeches that give him an opportunity to offer what could serve as a campaign agenda.

“The window is not closing. There will always be talented staff to get. You are dealing with a guy who has 90 percent popularity among Democratic voters. So why do people think that there has to be a rush?” said John Anzalone, a Democratic pollster who worked on the presidential campaigns of Barack Obama and Hillary Clinton. “The fact is that he is in an enviable position to take his time and get it right at all levels.”

Those close to Biden insist he is approaching the race less tactically — thinking about campaign staffers or early-state visits — and more thematically, on whether he can bring together factions in the party and convince primary voters that he’s the most electable against President Trump.

Some of his advisers don’t consider his age — he is 76 and on day one would be the oldest president ever to sit in the Oval Office — to be a prohibitive factor and insist that when voters see him on the campaign trail, they won’t either.

His wife, Jill Biden, who has been opposed to some past presidential runs, is said to be supportive.

While Biden has blown his self-imposed deadlines, those close to him say he simply believes he can wait to make a decision — and it could be an advantage.

The candidates who have made official announcements have more of a need to introduce themselves to voters and build a campaign network. Hillary Clinton, they note, did not announce her campaign until April 2015.

There are few modern-day parallels for someone like Biden — a man who has been considered a top-tier presidential candidate over such a long period, who almost always considers it and sometimes also runs.

“Joe has certainly taken it seriously and gone through the process and knows what it feels like,” said Larry Rasky, who has known Biden for decades and worked on both of his presidential campaigns. “When it feels right and when it feels wrong.”

Other candidates have run multiple times — William Jennings Bryan in 1896, 1900 and 1908, and former California governor Jerry Brown in 1976, 1980 and 1992. The man who could certainly match Biden’s longevity in presidential politics may be Henry Clay, who starting in 1824 ran multiple times over a quarter century.

“I’m not sure there’s an analogy. He’s a bit unusual in the sense that he’s had a very long career in American politics, has always been relevant, often is a front-page news story,” said Douglas Brinkley, a presidential historian. “There seems to be a constant question of, ‘What’s Joe going to do?’ He’s always plausible.”

“The downside is he always seems to be hemming and hawing,” he added. “It’s hard to develop momentum when you’re fence-sitting.”

The first time Biden weighed whether to run for president was in 1980, when a group of consultants approached him and outlined a case for his candidacy: President Jimmy Carter and Sen. Edward M. Kennedy would so bruise each other in the Democratic primary that he could emerge as the compromise candidate. A network was awaiting him in New Hampshire.

Ultimately, he took a pass.

Four years later, he went so far as to sign filing papers to compete in the New Hampshire primary, leaving them with his sister Valerie while he went on a vacation. On the flight to the Virgin Islands, he and Jill discussed the possibilities. By Biden’s retelling, he wasn’t convinced he was ready and, as soon as the plane touched down, he called his sister and told her not to file the paperwork.

In 1988, he openly struggled with the decision, telling reporters over and over that his time on the campaign trail would take away from his ability to be chairman of the Senate Judiciary Committee. Just before announcing he was running, he later wrote, he confessed to his wife that he didn’t want to do it. She urged him to go forward with it, given how many people’s lives he had put on hold.

“Jill, who had been so wary, had come to appreciate the sacrifices other people were making on our behalf,” Biden wrote in his 2007 memoir, “Promises to Keep.” “It was too late to change my mind.”

But his campaign struggled and less than four months after he got in, he dropped out, over allegations that he plagiarized a speech from a British politician.

Those who have known Biden over the years say he felt pulled into the 1988 campaign, listening more to those around him than his gut instincts, and the experience made him gun-shy. For the next several presidential campaigns, he did not consider running.

He spent months in deliberation over whether he would run in 2004, with those around him growing exasperated by his delays and with him growing exasperated by their exasperation.

“If I do this, I’m not going to do this on anybody’s terms but my own this time,” Biden told Gannett News Service. “If it’s too late, it’s too late. So be it.”

He never got in. He ran in 2008 but dropped out following a 1 percent finish in the Iowa caucuses. His political career was revived that same year when he became Obama’s vice president.

Ahead of the 2016 campaign, he was deeply conflicted and mourning the death of his son Beau. He ultimately announced in the Rose Garden that he would not run.

“I regret it every day,” he said later.

Some who have spoken recently with Biden say he is leaning toward a run but the decision is not firm enough to ask for commitments from donors or political activists. Biden also has told other candidates not to wait for him as they make their decisions.

“When he’s ready, he’s ready,” said one confidant. “He doesn’t like to be rushed. And the older he’s gotten, the less he likes to be rushed. And that’s what’s going on. He knows there’s a potential price to pay for waiting, but he’s going to do that rather than feel rushed.”