WASHINGTON — Janet L. Yellen told friends in recent weeks that she did not expect to be nominated as the next chairman of the Federal Reserve. Although she had been the Fed’s vice chairman since 2010 and would make history as the first woman to hold the job, President Obama’s aides made clear throughout the summer that he wanted Lawrence H. Summers, his former chief economic adviser.

Now, awkwardly, it appears that the president may have to circle back to Ms. Yellen after Mr. Summers withdrew from consideration on Sunday, bowing to the determined opposition of at least five Senate Democrats. On Monday, Ms. Yellen became the front-runner by elimination, officials close to the White House said.

Supporters of Mr. Summers, including many of the president’s closest advisers, had raised some concerns about Ms. Yellen in recent months. Perhaps most potently, they said that institutions benefited from fresh leadership and argued that Ms. Yellen’s crucial role in creating the Fed’s current policies could inhibit her ability to make necessary changes.

Some presidential advisers also argued that Mr. Summers brought crisis management experience and a working knowledge of financial markets that Ms. Yellen lacks — although so did Ben S. Bernanke when President George W. Bush selected him as chairman.