Washington (CNN) Vice President Joe Biden has extended his window for deciding whether to jump into the 2016 presidential campaign, several Democrats say, allowing the contest to play out even longer before he answers one of the biggest questions hanging over the race for the White House.

He is not preparing for the first Democratic debate on October 13 in Las Vegas and is not expected to participate, people close to him say, because he feels no pressure to reach a decision by then. He is likely to reveal his plans in the second half of October.

For more than two months, Biden has been studying the mechanics of what it would take to launch a candidacy. He and his team have been inundated by mounds of research and battle plans, but his original end-of-summer deadline passed without him reaching a conclusion.

Campaign managers in key early-voting states have already been identified. Dozens of major donors have stepped forward. Domestic and foreign policy advisers are waiting in the wings.

The speculation about Biden's future has reached a fever pitch, fueled by Democrats searching for an alternative to Hillary Clinton or a backup plan in case her candidacy falters. But with every passing week, many Democrats close to Biden are hardening in their beliefs that he will ultimately decide against challenging Clinton and the rest of the party's field.

He has stopped short of asking his advisers to actually pull the trigger on any of their plans-in-waiting, including setting up the legal structure of a campaign organization and taking steps to qualify for ballots in Michigan, Texas and other states with early deadlines.

"Nothing is actually being done yet," said a senior Democrat who has spoken with Biden, speaking to CNN on condition of anonymity to avoid openly violating the trust of the vice president. "There's far more talk than action."

Biden has said he would only run if he was certain he had a path to victory, several Democrats who have spoken to him say, a hurdle that he increasingly believes is within reach. But he is still unsure whether he and his family are ready for the campaign's emotional toll, these Democrats say, which he has said is the chief benchmark for running.

Yet in conversations with nearly two-dozen Democrats close to Biden, the same caveat emerges: He simply hasn't made up his mind. His closest circle of advisers is small enough to fit around his kitchen table and Biden is keeping limited counsel on this decision, which is why several people close to him urge caution against prejudging his final decision.

Sen. Tom Carper, a Delaware Democrat, who has known Biden for decades and served alongside him in the Senate, said he believes the vice president is growing closer to a verdict. But he said the timeline isn't as imminent as it once seemed.

"If you would have asked me several months ago, I would have said he should decide by the beginning of October," Carper told CNN. "But as time goes by, his numbers continue to improve and more and more people want him to run. I don't think he has to do something this week. This month? Yeah."

While Clinton has gone to great lengths to give the vice president space to make his decision, some of her loyalists quietly wonder whether the growing chatter about a Biden candidacy has contributed to an erosion of support in recent weeks. Some even go as far as suggesting that Biden could be playing the role of a spoiler.

When asked about that in an interview this week, Carper laughed: "Spoiler? I'm sure a few people might think that. But he has a lot of support and affection. He's giving it a lot of thought and hearing from a lot of people."

In the next breath, Carper asked: "When is Hillary's hearing?"

He was referring to Clinton's Oct. 22 appearance before the House Select Committee on Benghazi, which is investigating the 2012 terrorist attacks that killed four Americans. The private email account she used as Secretary of State is the subject of scrutiny at the committee and Justice Department.

To be sure, Carper said he did not know whether the Benghazi hearings would factor into Biden's decision. Other Democrats who are pushing Biden to run say that is one of the factors he is watching carefully, but acknowledge that he has to make up his own mind.

Sen. Tim Kaine of Virginia, a former chairman of the Democratic National Committee and Clinton supporter, said Biden still deserves time to announce his intentions. He said he did not believe Biden's process has damaged caused Clinton political damage.

"I don't think he's trying to artificially take more time than he needs," Kaine said in an interview this week. "You have to respect his timing, but as days go by, some things get harder for him -- practical things like getting on the ballot."

The prospect of Biden jumping into the 2016 race has been a lingering question -- and, at times, a punchline -- from late-night television shows to his appearances this week at the United Nations.

The Danish Foreign Minister slipped on Tuesday and referred to Biden as "Mr. President." He quickly corrected himself, adding: "Well, could have been! Can be! Who knows? If you have ... news to tell us here, please let us know."

The Biden decision is the biggest uncertainty on the Democratic side of the presidential race. His deliberations, which have unfolded in an unusually public fashion over the last two months, have drawn more people to his side through the Draft Biden movement, which has exploded with interest in early-voting states and across the country.

"I love Joe Biden because of his honest and authenticity," said Jon Cooper, national finance chairman of Draft Biden. "At the end of the day, if he were to say no, I would absolutely understand. But I'm the eternal optimist. I'm absolutely convinced he's running."

Some donors who have met with Biden have walked away absolutely convinced he is running, while other longtime friends seem equally certain he will not.

But Biden has been uncharacteristically quiet about his decision, according to several people who chatted with him in recent weeks at the Naval Observatory, his official residence. He rarely weighs the pros and cons of a run in public, they say, but seems more eager to be surrounded by familiar faces as he continues to grieve his oldest son Beau, who died of cancer only four months ago.

The collection of people who are directly involved in the deliberations is small, including: Steve Ricchetti, his chief of staff; Mike Donilon, an adviser for more than three decades who returned to the vice president's office a few months ago; Ted Kaufman, his longtime Senate chief of staff who briefly succeeded Biden in the Senate; Valerie Biden Owens, his sister and longtime strategist. Greg Schultz, the vice president's political director, has been assembling a campaign team should Biden decide to run.

The best guide to Biden's thinking, several people close to him say, can be found by carefully studying his own words, rather than listening to the growing chatter about the possibility of his candidacy. In two televised interviews last month, he voiced skepticism about whether he was ready to plunge into another bid for the presidency.

"It's just not there yet and it may not get there in time to make it feasible to be able to run and succeed, because there are certain windows that will close," Biden said in a September interview with America magazine, a Catholic publication. "But if that's it, that's it. It's not like I can rush it."