The calls don't focus entirely on a Biden 2016 run — someone familiar with the vice president's calls this week said the conversations have focused on his family after his eldest son's death earlier this summer.
But Biden remains undecided about launching another bid and on the phone appears interested in feeling out the political realities of getting in the race. He's inquired about how long he can wait to get in the race and how much money he would need to raise.
He hasn't stopped political advisers, including longtime aide Mike Donilon, from exploring paths to a bid, including scoping out strategists in early voting states.
Still elusive, however, are large-scale efforts to put in place a campaign infrastructure in places like New Hampshire or Iowa.
"Not a word" is how Mary Carey Foley, a Biden supporter and friend in New Hampshire, described her interactions with the vice president recently. She last spoke to the vice president earlier this summer.
"I anticipate having a call with him soon," said James Smith, a South Carolina state legislator who's a supporter of Biden's, who nonetheless hasn't spoken to Biden since late June.
Amid the swirl of information about Biden's political plans there appears at least one truth: the vice president's supporters are still ardently hoping he'll run even though they appear to be hearing little from the man himself.
One person familiar with Biden's calls this week downplayed their significance, noting the vice president "makes calls all the time."
Some of his discussions have been with longtime political consultants, though Biden's decades-long career in Washington means many of those consultants are also close friends.
Those who know Biden say it's doubtful that intricate political strategy has yet entered into his thinking about the race, though his aides and allies are openly discussing the logistics of mounting a bid.
"I don't believe he is evaluating the poll numbers or pragmatic political issues," said Dick Harpootlian, the former chairman of the South Carolina Democratic Party who's a longtime Biden backer. "He's evaluating where he is emotionally."
But the fact he's still deciding — and hasn't ruled out a bid outright — has supporters hopeful.
"The fact it's still being evaluated is encouraging," Smith said, adding he didn't see any rush for Biden to join the race. "As time goes on there appears to be a bigger and bigger space in the Democratic primary for him to step into."
If he does decide to run, Biden would enter a Democratic field where Clinton still holds a commanding lead, despite signs that Sanders is collecting support.
A CNN/ORC survey
taken in Iowa between August 7 and 11 showed Clinton the choice for 50% of likely caucusgoers. Sanders stood at 31% while Biden appeared at 12%.
The poll suggested Clinton would enjoy the biggest boost if Biden doesn't jump in the race — 58% of his supporters would back Clinton and 32% would back Sanders.
A New Hampshire poll
conducted by Franklin Pierce University and the Boston Herald showed Clinton behind Sanders in that state. Biden had 9% support from the sidelines without a campaign.
Far behind in those early primary and caucus state polls is former Maryland Gov. Martin O'Malley, although he said at the Iowa State Fair Thursday he'd welcome the company in the race.
"I sure would," said O'Malley. "I think Vice President Biden is a tremendous public servant for our country and I would welcome his entrance into this race. I think that the more voices for progress that people in our party hear from I think the better our party will do in general."
Another poll by Gallup showed 45% of Democrats nationwide want Biden to run for president; 47% said they didn't want to see the vice president mount a bid.
Among those encouraging against a run: former Vermont Gov. Howard Dean, who himself ran for the Democratic nomination in 2004 and later served as chairman of the Democratic National Committee.
"He's a very good guy and probably has no appeal whatsoever to people under 35," Dean said on NBC Thursday.
"I think it makes sense to have a candidate, and I think Hillary is one, I think Bernie is another who can really turn on the under-35 set, and I think that would be a problem for Joe," he said.
Sen. Claire McCaskill was similarly skeptical of a Biden run, telling Yahoo News
this week while Biden is a "sweet, nice guy," he wouldn't necessarily make a formidable opponent for Clinton.
"I'm worried if he does and doesn't do well, it will be hurtful to him, and we all care about him deeply," McCaskill said.