Janet Yellen, the lead candidate to succeed Federal Reserve Chairman Ben Bernanke, brings a demanding and harder-driving leadership style to the central bank, in contrast to Mr. Bernanke's low-key and often understated approach.

Ms. Yellen, the Fed vice chairwoman, is highly regarded by many central bank staff members, who call her an effective leader with a sharp mind. But she has clashed with others and left some hard feelings in the wake of those confrontations, according to interviews with more than a dozen current and...