[Roger W. Ferguson Jr.]'s announcement came just three weeks after Ben S. Bernanke succeeded Alan Greenspan as Fed chairman and leaves the Fed without the crisis-management experience of the top two officials who had led the central bank through international financial turmoil and terrorist attacks over the past eight years.

Greenspan and Ferguson "clicked so fast," recalled Gene B. Sperling, a [Bill Clinton] economic adviser who headed the administration's search for Fed nominees. Greenspan had never heard of Ferguson, but after working with him for just a few weeks, Greenspan called Sperling to say: "Ferguson's great. He's not just okay, he's terrific."

Ferguson, however, has disagreed publicly with Bernanke on one issue. Ferguson has opposed establishing a numerical target for inflation for several reasons, including the danger it would limit the Fed's flexibility. Bernanke has argued for years that a formal target would make Fed policy more effective.