Robert Rubin seemed an unusual choice to join the Clinton administration. His boss, Bill Clinton, won the presidency by running a populist campaign and Rubin, as co-chairman of Goldman Sachs, was hardly a populist. But the urbane, talented Rubin played an essential role in the new administration, first as the founding director of the National Economic Council, which he turned into a White House power center. Then, from 1995 to 1999, he was Treasury Secretary as the administration pressed Ch