Janet Yellen, the Federal Reserve's powerful vice chair, is by far the most likely candidate to replace Ben Bernanke when his second term at the helm of the U.S. central bank ends early next year, according to a Reuters poll of economists. The poll found that an overwhelming 40 of 44 economists said Yellen, the former president of the San Francisco Federal Reserve Bank, will take over for her boss in February 2014. Support for her nomination was strong but less decisive, with 23 of 38 economists backing Yellen's bid for the top job. Yellen, a 66-year old economist who is seen as a monetary policy dove, has held the No. 2 spot at the central bank since 2010. She has been a forceful advocate of the aggressive steps taken under Bernanke to spur U.S. economic growth and boost employment. "If President Obama nominates Janet Yellen, it would be a feather in his cap, as the first president to nominate a female Fed chairman," said Ellen Zentner, an economist at Nomura.