Washington (CNN) Joe Biden is poised to decide in the coming month whether he will jump into the Democratic presidential race, inching closer to answering the looming question of whether he will make a third bid for the White House.

One ally who spoke with Biden in recent weeks said that the former vice president indicated he was leaning toward a run. But if he reached a decision over the holidays, which he once indicated he hoped to do, he has not informed even his closest allies.

"He understands that he needs to make a decision relatively early in the process," the Biden ally told CNN, speaking on condition of anonymity to discuss private discussions. "He knows he can't wait."

Biden's silence has raised questions among some Democratic donors and activists about whether he is ambivalent about running and uncertain about plunging his family into a bruising campaign, despite friends saying Biden has repeatedly argued he is the party's strongest candidate to defeat President Donald Trump.

If Biden decides to run, he is likely to make a formal announcement later this winter or even early spring. On Election Day last November, Biden told reporters that even if he were to make a decision in early January, he would wait to reveal his answer.

"I wouldn't announce even if I were going to run that early. It'd be too early to get started," he said, adding that the timing "would depend on the circumstances in the field and a whole lot of things."

But most of those factors -- particularly the timing -- are not squarely in his control. The race is already underway and he is facing pressure from some donors to signal his intentions and begin articulating how he would navigate a crowded Democratic primary field.

The former vice president is set to return to Washington this week. His public schedule for the month so far remains light -- a stop in Texas on January 24 to promote his book, "Promise Me, Dad" and an event billed as "An Evening with Vice President Joe Biden" in Fort Lauderdale, Florida, on January 28.

Biden last spoke publicly about his timing during a stop on his book tour in early December, setting a window of six weeks to two months. And now, that self-imposed deadline is quickly approaching as Democrats anxiously await Biden's verdict.

If he decides against running, as he ultimately did in 2015 after openly flirting with challenging Hillary Clinton for months, several donors and longtime supporters are eager to get behind other candidates in one of the most wide-open, unwieldy races in the history of the party.

One longtime supporter said conversations among Biden loyalists revolve around this simple question: Would his announcement day be the best day of his campaign?

While Biden is leading the early field of Democratic contenders, largely because of name recognition after serving alongside President Barack Obama for eight years, his politics do not necessarily match the progressive energy coursing through the party.

It would be Biden's challenge to persuade Democratic activists that he, at age 76, is best equipped to defeat Trump when the Democratic Party is rallying around younger and more diverse candidates.

Sen. Elizabeth Warren's first Iowa campaign trip of the year this weekend has heightened the need for Biden to make a decision, several Democratic activists say, with some Biden supporters taking matters into their own hands and volunteering to join a campaign-in-waiting.

"Oh my God. I can't wait," said Mary Carey Foley, a longtime supporter who described herself as a "walking billboard in New Hampshire" for Biden. "I need a project, and he'll be it if he's decided to go for it."

But other admirers in key early voting states are eager to see whether he's serious about a run.

"If Biden is in, I'm with Biden. If Biden gets out, then I'll start looking around," said Tony Bisignano, an Iowa state senator, and longtime supporter. "I would hope that if he is really serious and doing some background work right now in his preparation that at least some signal would be sent that he's looking at it, but he hasn't made a decision."

But some former Biden supporters in Iowa said they're not ready to sign on to a bid before the former vice president has made a decision.

"If he said, 'Hey, I'm going to do a run this time,' I probably would lean towards supporting him again, but it's a little premature," said Lisa Heddens, an Iowa state representative who supported him in 2008.

"I think there would be a lot of things to recommend him, but he has to make his decision first," said Herman Quirmbach, an Iowa state senator, who signed on to the Draft Biden movement in 2015.

A staple in Democratic politics for nearly a half-century, Biden has strong connections with many Democratic activists in early voting states and beyond. His two presidential campaigns, in 1988 and 2008, ended poorly. But being selected as Obama's vice president elevated his standing as a beloved favorite among many in the party.

Yet that hardly guarantees a glide path to the nomination.

"We've got a lot of people talking about running," said Steve Shurtleff, the speaker of the New Hampshire state House of Representatives and a former Biden supporter. "At some point I would endorse somebody, but we have a long way to go."

Shurtleff said he received a call from Biden after he secured his party's nomination for speaker.

"The only thing I said was we look forward to seeing him at some point in New Hampshire," Shurtleff said. "He just laughed and said 'We'll see what happens.'"

James Smith, a friend of the Biden family and the former Democratic nominee for governor in South Carolina, said a member of Biden's team recently reached out to set up a phone call between him and the former vice president.

"I hope to speak with him soon," Smith said.

Biden spent part of his holiday in the Virgin Islands with his wife, Jill, taking time to contemplate whether to upend his life -- and potentially diminish his legacy -- with what could be the toughest campaign of his long career. He returned home with a smile but no definitive sign of his conclusion.

As he walked through the Philadelphia airport late Friday, he told CNN's Randi Kaye that he would make up his mind "soon."