Washington (CNN) Vice President Joe Biden met privately with Sen. Elizabeth Warren on Saturday in his residence at the Naval Observatory, CNN has learned, another sign he is seriously deciding whether to jump into the Democratic presidential race. 
 
 Warren and Biden discussed economic policy during a meeting that lasted about two hours, a person familiar with the discussion told CNN, adding that the presidential campaign or Biden's future was not a particular focus of the discussion. 
 
 The meeting, confirmed by two people familiar with the session, is the biggest indication yet that Biden is feeling out influential Democrats before announcing his intentions. 
 
 Beloved by liberal Democrats, Warren decided to sit out a campaign of her own, but she has yet to formally endorse a candidate. In an interview on Friday, she told WBZ in Boston: "I don't think anyone has been anointed." 
 
 The vice president arrived in Washington shortly before lunchtime, even though his official schedule said he was planning to spend the weekend at his home in Delaware. 
 
 Kendra Barkoff, a Biden spokeswoman, declined to comment on the meeting. But an aide to Biden confirmed a meeting, telling CNN: "The vice president traveled last minute to Washington, D.C. for a private meeting and will be returning to Delaware." 
 
 Another source familiar with the meeting told CNN that Warren went to the meeting at Biden's request. 
 
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 Biden is increasingly weighing whether to challenge Hillary Clinton and other Democratic candidates for the party's presidential nomination. A small team of advisers has spent weeks quietly putting together a campaign strategy and fundraising plan in case Biden decides to run. He had at least one meeting with them this week in Wilmington, one person familiar with the session told CNN. 
 
 He has told his associates he intends to make his decision in the next month, an announcement that could upend the fight for the Democratic presidential nomination. 
 
 With the Iowa caucuses and New Hampshire primary six months away, Biden is the leading figure Democrats believe they could turn to if they needed to find an alternative to Clinton, whose favorability ratings have taken a deep hit as her email use while secretary of state is drawing deeper controversy. 
 
 Biden, 72, has a large and loyal collection of friends and advisers from more than four decades in Washington. Yet even inside his sprawling constellation, affectionately known as "Biden World," deep divisions exist over the wisdom of him making another bid for the presidency. 
 
 Mapping out the steps 
 
 Earlier this week, Biden met with top advisers at his home in Delaware to further map out the steps to mounting a third presidential bid, though people familiar with the confab say the vice president is no closer to deciding on a run. 
 
 Biden met with his political team in Wilmington, where he spent the last week out of sight following a vacation in South Carolina. Longtime political allies Mike Donilon and former Sen. Ted Kaufman were among the operatives advising Biden on a run, a person familiar with the meeting said. 
 
 The factors Biden continues to mull include a timeline for getting in the race, and a fundraising plan that could help him launch a come-from-behind campaign against Clinton. 
 
 Photos: Photos: Vice President Joe Biden Photos: Photos: Vice President Joe Biden U.S. Vice President Joe Biden began his career in politics in 1972, winning election to the Senate at the age of 29 (he was 30 when he took office). The Delaware Democrat was reelected to the Senate six times, including 2008, before becoming the 47th vice president of the United States. Hide Caption 1 of 14 Photos: Photos: Vice President Joe Biden Biden is sworn in for his second term as vice president by Supreme Court Justice Sonia Sotomayor, with his wife, Jill, and son, Beau, by his side, on January 21, 2013, in Washington. Hide Caption 2 of 14 Photos: Photos: Vice President Joe Biden Biden presides over a ceremony in Baghdad to formally mark the end of the U.S. combat mission in Iraq on September 1, 2010. Hide Caption 3 of 14 Photos: Photos: Vice President Joe Biden Biden and President-elect Barack Obama wave to the crowd at their election night party at Grant Park in Chicago on November 4, 2008. Hide Caption 4 of 14 Photos: Photos: Vice President Joe Biden Biden speaks after being introduced as Obama's running mate while campaigning together after the Democratic National Convention in 2008. Hide Caption 5 of 14 Photos: Photos: Vice President Joe Biden From left, former Sen. John Edwards, Biden, Obama and Sen. Hillary Clinton at a debate of Democratic presidential candidates on April 26, 2007, in Orangeburg, South Carolina. Hide Caption 6 of 14 Photos: Photos: Vice President Joe Biden Biden releases his memoir, "Promises to Keep: On Life and Politics," in 2007. Hide Caption 7 of 14 Photos: Photos: Vice President Joe Biden As a ranking member of the Senate Foreign Relations Committee, Biden is interviewed on NBC's "Meet the Press," concerning the war in Iraq on August 14, 2005. Hide Caption 8 of 14 Photos: Photos: Vice President Joe Biden While chairman of the Senate Foreign Relations Committee, Biden meets Afghan students during a visit to Kabul in 2002. Hide Caption 9 of 14 Photos: Photos: Vice President Joe Biden Biden is welcomed back after undergoing surgery for an aneurysm in 1988. Hide Caption 10 of 14 Photos: Photos: Vice President Joe Biden Biden announces his candidacy for the Democratic presidential nomination in 1988. After three months he drops out, following reports of plagiarism and false claims about his academic record. Hide Caption 11 of 14 Photos: Photos: Vice President Joe Biden While on the Senate Judiciary Committee, Biden meets with Sen. Frank Church, center, and Egyptian President Anwar Sadat after the signing of the Egyptian-Israeli Peace Treaty in 1979. Hide Caption 12 of 14 Photos: Photos: Vice President Joe Biden President Jimmy Carter and Biden attend a reception for the Delaware Democratic Party in 1978. Biden was the first senator to endorse Carter's presidential candidacy two years earlier. Hide Caption 13 of 14 Photos: Photos: Vice President Joe Biden At a convention in 1972, Biden and his first wife, Neilia, and his two sons take a photo with Delaware Gov.-elect Sherman W. Tribbitt and his wife Jeanne. Neilia Biden died in a car accident a few months later, after his first election to the Senate, along with their infant daughter, Naomi. Hide Caption 14 of 14 
 
 Like many Democrats, Biden and his team are carefully eyeing the continued questions about Clinton's email use at the State Department. Developments this week, including allegations that classified information may have passed through her private account, have led to new anxiety within the Democratic Party about the frontrunner's viability. 
 
 Those jitters haven't necessarily led to widespread calls for Biden to join the race; at the White House, there is some concern a Biden candidacy could end poorly and damage the vice president's reputation. 
 
 But with polls showing Clinton's trustworthiness slipping, some top Democrats are looking elsewhere. 
 
 "Frankly when it became clear that he was giving the race serious consideration, I just raised my hand," Steve Schale, who ran President Obama's 2008 and 2012 campaigns in Florida, told CNN on Wednesday. Last week Schale joined "Draft Biden," the independent group encouraging the vice president to run. 
 
 Draft Biden, which began earlier this year as a bare-bones effort to rally support behind Biden, has recently morphed into a full-fledged organizing campaign, including robust fundraising efforts, that could provide a framework for Biden should he jump into the race. 
 
 Costs of running 
 
 Biden's advisers have told the vice president he must decide by Oct. 1 -- roughly a week after his self-proclaimed "end-of-summer" deadline. A top Biden adviser told CNN this week the vice president is expected to wait at least until mid-September to announce a decision. 
 
 If Biden does mount a run for president, the cost of flying him from event to event on Air Force Two would come under scrutiny, as political travel for sitting presidents running for re-election has for decades. 
 
 Current regulations enacted during the last presidential election stipulate a candidate must reimburse the government for a pro-rated share of an equivalent-sized charter plane. 
 
 Biden often flies in a C-32, the military analogue to a Boeing 757. The cost to charter a 757 is between $12,000 and $15,000 per hour, according to charter companies. 
 
 That's far less than the actual costs to fly Air Force Two, which comes retrofitted with secure communication and navigation equipment, and costs north of $100,000 to operate per hour. 
 
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 Travelers who must reimburse the government for political trips include the candidate and any staff traveling on behalf of his campaign. Other passengers, including security personnel, aren't required to reimburse the government for their portion of the trip. 
 
 The goal of the regulations: to ensure the costs of an office-holder's travel requirements neither hinder nor help a candidacy. 
 
 If he runs, Biden could combine campaign trips with official travel to mitigate the costs, which presidents have done for decades. The formula breaking down campaign and official costs, however, has been kept secret by White Houses going back to the 1970s. 
 
 The distinction between official and political travel has also been blurry in the past. Official travel requires the president or vice president to be advancing or explaining the work of the administration -- and as vice president, much of Biden's campaign pitch would entail doing just that. 
 
 Clinton has traveled using a mix of commercial and private air, none of which is nearly as large as a Boeing 757. The Gulfstream G500 she flew to Martha's Vineyard in on Saturday costs between $7,000-$8,000 to charter per hour. 
 
 But she or her campaign must foot the bill for the entire flight, not only a pro-rated portion of it, or a percentage split with official travel. Unlike Air Force Two, the government assumes none of the costs. 
 
 In her first quarterly FEC filing from July, Clinton's campaign reported spending almost $134,000 on a single private jet service, Executive Fliteways. 
 
 As a former first lady, Clinton travels with a Secret Service detail, though its footprint appears far smaller than Biden's. The Secret Service is not reimbursed for any costs associated with political travel. ||||| Photo 
 
 Vice President Joseph R. Biden Jr. on Saturday summoned Senator Elizabeth Warren, Democrat of Massachusetts, to his Washington residence for a meeting, the latest indication that he is seriously considering a presidential bid. 
 
 Mr. Biden and Ms. Warren met for lunch on the veranda at the Naval Observatory with no aides present, according to a Democrat briefed on the conversation. 
 
 The conversation, which lasted for well over an hour, touched on policy issues and both the Republican and Democratic presidential primary campaigns. Mr. Biden made clear that he was seriously considering a bid of his own, but did not directly ask Ms. Warren for her support. 
 
 The discussion about what has been an unpredictable presidential campaign — in which Senator Bernie Sanders of Vermont has shown strength on the left and Donald J. Trump has emerged as a force on the right — centered on “what the country is trying to tell us,” said the Democrat briefed on the lunch. 
 
 Mrs. Warren was the dream presidential candidate of many progressives and still retains a loyal following among liberal activists. 
 
 The meeting comes as Mr. Biden — whose eldest son, Beau, died in May — has begun to intensively test the waters for a third White House run, meeting with his small inner circle and telephoning Democratic donors. 
 
 The meeting Saturday, first reported by CNN, came at Mr. Biden’s request this week. 
 
 An aide to Mr. Biden said only that he returned at the “last minute” to Washington and then planned to travel back to his home state of Delaware, where he has gathered with relatives and advisers over the last week. 
 
 Ms. Warren has helped set the agenda for progressive policy in her brief time in the Senate, and has become a favorite of the left for her fiery rhetoric against financial institutions. 
 
 She told WBZ-TV, a Boston station, on Friday that no one “has been anointed” for the Democratic nomination. 
 
 Ms. Warren met near the end of last year with Hillary Rodham Clinton, the leading candidate in the polls for the Democratic nomination. But Ms. Warren and Mrs. Clinton are not natural allies, and they have had a sometimes tense relationship over the years. 
 
 Mrs. Clinton has also seen her personal favorability ratings dip amid questions about her use of a private email server during her time at the State Department, and Mr. Biden’s allies are watching to see what happens with that issue as he weighs his decision, which may not come until well into September.
– In what's being called the biggest indication that he's considering jumping into an already crowded presidential race, Joe Biden invited lefty darling Elizabeth Warren over to his DC residence for a lengthy and cozy lunch yesterday, reports CNN. The two talked economic policy and the Democratic and Republican primaries, and though Biden made clear he's considering a run, the New York Times notes that he did not directly ask Warren's support. Warren, who eschewed a run of her own, has yet to back any candidate, Friday telling WBZ in Boston that "I don't think anyone has been anointed." The Times notes that Warren and Hillary Clinton "are not natural allies" and have crossed swords often. Biden is expected to make a decision within a month.