A fund-raiser for Barack Obama, Hillary Clinton and other Democrats who was charged last week with defrauding Citigroup also defrauded other banks, U.S. prosecutors said. The allegations against fund-raiser Hassan Nemazee—arrested last week on a bank fraud charge and released on $25 million bail—were not formal charges but were in a letter dated Tuesday from prosecutors to a Manhattan federal court magistrate judge handling the case. Nemazee, 59, head of a private equity firm, was accused on Aug. 25 of one count of bank fraud for seeking a fraudulent $74 million loan from Citigroup's banking unit. He said after his...