With time running out on a Thursday deadline to avert a historic default on the nation's debt, some policymakers are starting to ask, where is Vice President Joe Biden?
Biden played a prominent role in negotiating an agreement that averted a debt default in August 2011. This time around, though, he has been largely absent from budget negotiations on Capitol Hill.
(Read more: White House: 'We're far from a deal')
Talks so far have been between Senate Majority Leader Harry Reid, D-Nev., Senate Minority Leader Mitch McConnell, R-Ken., and House Speaker John Boehner, R-Ohio. But divides between the congressional leaders have obstructed any real progress on a deal.
Sen. John McCain, R-Ariz., recently complained that Biden, who spent decades in the Senate and has a reputation as a dealmaker, has been nowhere in sight.
"Maybe we need to get Joe Biden out of the witness protection program because he has good relationships" with lawmakers, McCain told CBS' "Face the Nation."
Under the Constitution, the vice president serves as president of the Senate. He may vote there in the case of a tie but is not required to. Instead of camping out with Senate leaders, Biden and wife Jill headed to Camp David on Saturday for a three-day holiday weekend.
Biden was scheduled to participate in budget talks Monday between President Barack Obama and congressional leaders, but the White House said the meeting was postponed to give Senate leaders more time.
Criticism that Biden hasn't done enough to help resolve the crisis might be unfounded, though, at least when taking U.S. history into account. Historically, vice presidents have played a limited role in Washington politics, said Joel K. Goldstein, a law professor at St. Louis University and leading authority on the office.
When Abraham Lincoln was first elected president in 1860, for example, Vice President Hannibal Hamlin attended his inauguration in Washington and then returned to his home in Maine. In fact most every vice president, from Thomas Jefferson to Millard Fillmore, didn't view getting involved in the legislative process as part of the job, Goldstein said. Most vice presidents would be in D.C. for the congressional session and in their home state for two-thirds of the year.
Walter Mondale, who served as 42nd vice president to President Jimmy Carter from 1977 to 1981, changed the office from being more or less a figurehead position to one actively involved in policymaking, Goldstein said.
Mondale was the first vice president to secure an office in the White House, for example, and he established the right to attend meetings and access official documents. He also initiated the tradition of weekly lunches with the president.
"All of those factors have taken an office that, for most of our history, was pretty insignificant and turned it into a really quite robust political institution," Goldstein told CNBC.com. "What's happened has been that the Mondale vice presidency really created a new model and a set of expectations, and all of his successors have basically inherited the resources that Mondale got for the office."
All vice presidents since have continued Mondale's activist approach, Goldstein said.
Al Gore, who served as No. 2 to President Bill Clinton from 1993 to 2001, was deeply involved with budget negotiations during the last government shutdown, Goldstein said, adding that Gore "added some more steel to Clinton's spine" during talks with the GOP.
Dick Cheney, who served as vice president to George W. Bush during his two terms (2001-09), used the power of the office to the point that some referred to him as a shadow president.
From Cheney's negotiations leading to the 2001 and 2003 tax cuts to the reauthorization of the warrantless surveillance program in April 2004, Goldstein said there are many examples of his "enormous influence."
For his part, Mondale told CNBC.com that he thinks Biden has been an "excellent vice president" and downplayed criticism about his involvement, or lack thereof, in the budget talks.
"This time around, the Senate is insisting on having a more separate role from the White House, so there may be a difference there [from how Biden handled past budget battles]," Mondale said. "But I'll bet a lot that he's in there with the president and working on this all the time."
From a historical perspective, Goldstein said, criticism that Biden hasn't done enough in the debt crisis isn't quite fair, especially as White House schedules show he has been attending meetings behind the scenes.
"Biden now seems to be playing a conventional role for vice presidents in the period since Mondale," Goldstein said. "What's distinctive isn't the role he's playing this time but the role he's played in the prior [budget battles], which was really, in many respects, unprecedented."
A request for comment from Biden's office was not returned.