Joe Biden's been quiet.

Aside from a stop-and-chat with CNN at the Philadelphia airport and a tweet condemning Rep. Steve King of Iowa, the former vice president has remained largely out of public view during the first couple weeks of the new year.

All around him swirl budding 2020 presidential candidacies: Elizabeth Warren's opening trips to Iowa and New Hampshire, Kamala Harris' book tour, Julian Castro's launch, Kirsten Gillibrand's announcement to Stephen Colbert on CBS' "The Late Show" on Tuesday night.

Meanwhile, Biden's largely kept his head down, with no travel booked to early primary states and few public sightings.

"He's been radio silent," says Dick Harpootlian, a South Carolina Democratic state senator and longtime Biden ally, "so I think he's deciding what to do."

There's a theory held by some Biden confidantes that the pressure to decisively dive into this presidential primary soon doesn't apply to their guy. He's Joe Biden, after all, the fun white-haired uncle with years of goodwill built up among Democrats of all stripes virtually everywhere. A Washington fixture for more than four decades and a two-time prior White House contender, Biden has the luxury to bide his time, to wait, the theory goes.

But Harpootlian doesn't think that's necessarily the theory held by Biden himself.

When he last spoke with him, at a gathering at a Washington restaurant in mid-December, Harpootlian says Biden "gave the sense that we'd hear something the first couple weeks of January, mid-January."

While Harpootlian is stone-cold certain that the day Biden announces "he's the odds-on favorite in South Carolina," he doesn't think his friend is immune to the timelines of the other circling would-be contenders, many of whom are nearing their own announcements, triggering a pronounced dash for staff, cash and, of course, Instagram followers.

"I'm for Joe if he declares in April," Harpootlian says. "But you've got folks coming through, picking up people, and you don't want people saying, 'I would've gone with you but I've committed to Kamala or Beto [O'Rourke] or Cory [Booker] or Elizabeth Warren."

There are also the ghosts of 2016 to consider, when the death of his son Beau postponed and ultimately denied him the ability to mount a campaign, emotionally and logistically.

"I believe we're out of time," he said in a Rose Garden declaration in October 2015, "the time necessary to mount a winning campaign for the nomination."

That experience hasn't been lost on other associates around Biden, who insist he hasn't fully made up his mind and believe there's a chance he could again pass up the opportunity.

"The difference between Joe Biden and these other folks is that when they say they don't know they're going to run for president, you know they're going to run for president," says a Biden adviser outside the inner circle but who stands ready to work for a potential campaign.

"He has not decided. I'm almost certain of that," says another former Biden adviser. "That doesn't mean he's not going to do it."

Several differences are at play this time around. At age 76 now, Biden would easily be the oldest president elected in U.S. history, a factor that also impacts the potential candidacy of Bernie Sanders, who is 77.

It means Biden would finish a first term at age 82, four years over the current average life expectancy for Americans.

More enticingly, as an elder statesman, he would be a front-runner this time, enjoying a polling advantage at the starting line that he never had ahead of 2016 or in either of his prior bids in 2008 and 1988.

Biden won 32 percent of the vote of likely Iowa Democratic caucus-goers in a poll taken a month ago, a field-leading number placing him 13 points ahead of second-place Sanders. Perhaps more significantly was that caucus-goers preferred a "seasoned hand" to a "newcomer" by a 13-point margin.

But his most potent allure is the perception he can defeat President Donald Trump, that he can withstand the nonsense, throw his own schoolyard punches when necessary and yet still inspire uplifting confidence in a polarized nation desperately looking to restore its better angels.

The attraction to his durable political pedigree is prompting a bevy of old guard Democrats to publicly pump up Biden.

Third-term New York Gov. Andrew Cuomo, who passed on a 2020 run, has said Biden's credibility offers "the best case" for Democrats, despite the fact that his home state senator, Gillibrand, is diving into the contest.

Similarly, Sen. Dianne Feinstein of California announced that Biden would be her candidate, too, even though Harris, her Senate colleague, is planning to get in the race in the coming days. "He brings a level of experience and seniority, which I think is really important," the 85-year-old Feinstein told reporters.

Recently defeated Sen. Bill Nelson said Biden would be his preferred candidate due to his chances of carrying battleground Florida, strengthened by the perception that he's "moderate enough."

And Harry Reid, the 79-year-old former Senate majority leader from Nevada, dubbed Biden the "front-runner at this stage. People are waiting to see what he's going to do."

"I think the establishment sees him beating Trump – and that's the only measure that matters," says Juleanna Glover, an adviser on The Biden Institute's policy board. "You could easily see Biden holding his own against Trump on the debate stage, whereas the others are untested and unvetted."

The question is if "electability" is antiquated thinking in an age when a reality television star was able to defeat a former secretary of state. There's the chance that Biden could get eaten up and spit out by the ascendant, aggressively liberal Democratic Party base, fueled by popular populist agitators like Rep. Alexandria Ocasio-Cortez of New York and her throngs of younger acolytes who aren't waiting to be asked for a seat at the agenda-setting table.

Biden would be forced to explain his actions from another era, in which he oversaw the hearings of Supreme Court Justice Clarence Thomas, heaped praise on William Barr, now Trump's nominee for attorney general, and worked to pass a crime bill that critics argue led to an epidemic of mass incarceration.

He will go through the ringer and is clear-eyed that the crowded nomination fight will be a slog, with potential for embarrassment. Failing in a third White House run at his age would be an enduring blemish on his legacy – a legacy that could alternatively end with his two-term run as a largely successful vice president and America's favorite uncle.

Those who have worked for Biden before believe that he won't let speculation drag on for months and that he'll make a decision soon. Given his predilection for unscripted remarks and moments, when and how he chooses to reveal that decision is another matter. Rather than as part of an overly polished, carefully calibrated rollout, he could just blurt it out at a time of his choosing – and still reap the media windfall.

He's scheduled to speak at Al Sharpton's National Action Network's Martin Luther King Jr. breakfast in Washington on Monday. He'll appear at a rescheduled book tour event in Dallas next Thursday. And the final week of the month finds him in Broward County, Florida, for a "moderated discussion," where the question will be inevitable if it hasn't been answered yet.

Biden looks ready to re-emerge in the conversation just as the Democratic primary begins to get busy. Facing an assembly of fresh faces, there's some advantage for the elder party statesman to keeping everyone guessing.