When Mr. Dudley took the helm in 2009, the financial crisis had left the New York Fed's reputation as a regulator damaged. The institution had not done enough to address the severe weaknesses at the banks it oversaw, like Citigroup. Early on, Mr. Dudley commissioned a review of the New York Fed's bank supervision department and then overhauled it. But in 2012, JPMorgan Chase, also overseen by the New York Fed, suffered huge trading losses in what was known as the London Whale scandal. The New York Fed was faulted.