Israeli central banker Stanley Fischer announced a formal bid to head the International Monetary Fund, positioning himself as a dark-horse candidate as the race enters its final stages.

"In normal times, you can probably rely on intuition," Mr. Fischer said in an interview. "But all the time, in different countries, there are serious economic issues" that need to be addressed, Mr. Fischer said, and IMF staffers often offer conflicting advice. "Without having that [economic] training, it's very hard to know who's right and...