Mr. Geithner and Mr. Summers, by contrast, have strong White House ties. Mr. Geithner has said he doesn't want the job; Mr. Summers is interested, according to people who know him, but he declined to comment.
While Mr. Bernanke doesn't appear to want a third term as Fed chairman, the president could press him to stay. Mr. Bernanke said in March he had discussed his plans "a bit" with Mr. Obama but declined to say more. The White House hasn't disclosed how the president will choose.
The selection involves more than political drama. The Fed could be entering another perilous period. The central bank has pushed short-term interest rates to near zero, launched bond-buying programs that pumped trillions of dollars into the economy and left its own $3 trillion securities portfolio swollen with mortgage-backed and Treasury securities.
At some point, the next Fed leader will need to use untested methods to reverse the process, raising interest rates and siphoning up huge volumes of cash from banks. "They will be learning as they go," said Laurence Meyer, a former Fed governor.
Ms. Yellen's supporters say there are few better prepared students. She was class valedictorian at Fort Hamilton High School in a middle-class Brooklyn neighborhood. Her father was a doctor who worked out of the basement of the family's brownstone. Her mother, who quit an elementary school teaching job to raise two children, drove him to house calls and managed the family's finances—tucking away savings and tracking stock prices from the afternoon newspaper in small, neat handwriting, said Ms. Yellen's brother, John.
"My parents held us to high academic standards," said John Yellen, the archaeology program director at the National Science Foundation. After dinner, he recalled, they listened to radio programs, including the adventure series, "Sergeant Preston of the Yukon."
Ms. Yellen got interested in economics in college. While an undergraduate at Brown University, she was impressed with a talk by visiting Yale professor, James Tobin, who would later win a Nobel Prize in economics. She decided to pursue an economics Ph.D. at Yale, where her interest in unemployment grew while working with Mr. Tobin, her mentor and dissertation adviser.
Mr. Tobin, a child of the Depression and an adviser to presidents John F. Kennedy and Lyndon B. Johnson, emphasized the human toll of high unemployment and the government's obligation to combat it. He was so impressed with her meticulous notes of his lectures that he asked her to turn them into a textbook. She left to teach at Harvard and didn't complete the book.
Willem Buiter, Citigroup's chief economist, said Ms. Yellen's notes were like the Old and New Testament for Yale Ph.D. students when he studied there in the 1970s. "She was a legend when I arrived at graduate school," said Richard Levin, Yale's president, who used them to study in the 1970s.
Ms. Yellen went to work on the Fed staff in the fall of 1977, where she met her future husband, economist George Akerlof. They married the following June. "Not only did our personalities mesh perfectly, but we have also always been in all but perfect agreement about macroeconomics," he wrote in an autobiography after he won the 2001 Nobel Prize for economics. Their son, Robert Akerlof, is an economist teaching at the U.K.'s University of Warwick.
Her husband is skeptical of markets. In a talk at last year at Warwick, he said, "the public and economists have too great an acceptance that whatever markets do is right."
Ms. Yellen climbed the Fed ranks by being methodical rather than iconoclastic. She shows up at policy meetings with carefully crafted statements. Those who work with her say she arrives at the airport hours early.
During the mid-1990s, then-Fed chairman Alan Greenspan asked her to take the lead in an internal Fed debate about whether to adopt a formal inflation target. Her preparation impressed others. "She does her homework," said Mr. Broaddus, her chief adversary in the debate.
During the discussion Ms. Yellen challenged Mr. Greenspan, who was rarely confronted, to define his views of price stability, according to Fed transcripts and people there. Later, as the economy strengthened, she worried about the booming stock market and also urged Mr. Greenspan to raise short-term interest rates to head off inflation—advice he declined, according to Mr. Meyer, her colleague at the time.
Ms. Yellen became chairwoman of the Council of Economic Advisers under President Bill Clinton in 1997, a period of strong economic growth. She and Clinton adviser Gene Sperling danced with their hands in the air at a 1999 White House staff meeting in the Roosevelt Room when the jobless rate fell near 4%, according to people at the meeting.
Later, as president of the San Francisco Fed, Ms. Yellen sounded early warnings about the danger of a U.S. housing bust. "I still feel the presence of a 600-pound gorilla in the room, and that is the housing sector," she said at a June 2007 policy meeting, according to Fed transcripts. "The risk for further significant deterioration in the housing market, with house prices falling and mortgage delinquencies rising further, causes me appreciable angst."
Three months later, she foresaw a dangerous economic cascade.
"A big worry is that a significant drop in house prices might occur in the context of job losses, and this could lead to a vicious spiral of foreclosures, further weakness in housing markets, and further reductions in consumer spending," she said, at a September 2007 meeting. "The potential effects of the developing credit crunch could be substantial."
In December, she called on the Fed to cut interest rates aggressively, according to Fed transcripts. Mr. Bernanke chose a more cautious approach—until a month later, when conditions worsened.
Shortly after the Fed rescued Bear Stearns Cos. in March 2008, Mr. Obama—then a senator and presidential candidate—called Ms. Yellen. He wanted explanations of the unfolding financial turmoil and she was among a few people he asked, said Austan Goolsbee, an Obama adviser who arranged the call.
Ms. Yellen, a Democrat, impressed Mr. Obama during a 30-minute conversation as she explained the risk of modern-day bank runs at Wall Street firms spreading like wildfire through markets, Mr. Goolsbee said.
She has ruffled feathers at the Fed with her strong views, but the central bank in the past three years has moved toward her prescription of sustained aggressive action.
As Fed officials deliberated last April about how long to keep interest rates low, Ms. Yellen delivered a 20-page speech, with 18 footnotes and 15 charts, making the argument that rates should stay low until 2015 or later. The speech, later praised by Mr. Bernanke, presaged a shift by the Fed toward making clear its intentions to keep rates down longer than previously planned.
"She argues very effectively," Charles Evans, president of the Chicago Fed said in an interview. "She is constantly asking you to think about the argument that you have put on the table, especially when it is at variance with other facts. People look to her and listen to what she's saying."
While the Fed's second-in-command traditionally stands in the shadow of the chairman, Ms. Yellen has been outspoken. Mr. Bernanke was closer personally to Ms. Yellen's predecessor, Donald Kohn, another potential successor, who formed a bond with the chairman during the crisis, said people who know them.
Still, Mr. Bernanke and Ms. Yellen largely see eye-to-eye. "I can't see a material difference between them," said another central banker who has seen them often at international meetings in Basel, Switzerland.
Last year, Ms. Yellen ran a Fed committee that crafted a document detailing how the Fed viewed its so-called dual mandate, the central bank's focus on both inflation and unemployment, as set by Congress.
The document for the first time made a formal 2% inflation target, a goal of both Mr. Bernanke, as well as inflation hawks—those who worry most about keeping prices stable. It also laid out markers for unemployment rates, which the hawks resisted.
Officials haggled over the 531-word document for months, according to people involved in the discussions. The Fed directly controls inflation through its management of the money supply, but many factors influence unemployment. Officials were wary of promising too much on hiring, and they struggled to define how they would balance job goals with inflation.
The document illustrated Ms. Yellen's view of Fed operations. As long as inflation was running below 2%, she argued, the Fed could afford to keep money flowing, helping bring down unemployment.
Ms. Yellen also pushed for more than a year behind the scenes for another step to signal the Fed's commitment to low rates, said people involved in the debate. In December, following the advice of her and Mr. Evans, the central bank promised to keep short-term interest rates near zero until the jobless rate falls to 6.5%, as long as inflation doesn't threaten to rise any more than a half-percentage point above the 2% goal.
The moves create a framework for an exit plan: As the job market improves, the central bank will gradually stop its bond buying. Later, after unemployment falls to 6.5% or lower, the Fed will start raising short-term interest rates.
If inflation ticks up, it might move sooner. Eventually, the Fed could sell some of its bonds and begin soaking up all that cash.
It will be up to the Fed's next leader to prove the plan will work.