One day before Whitewater hearings were set to begin in Congress, President Clinton reaffirmed his support for his embattled Deputy Treasury Secretary, Roger C. Altman. The once heir apparent to the top spot at Treasury has been under fire since February, when he acknowledged dubious meetings between federal regulators and White House officials regarding the investigation of Whitewater. Altman's frequently changing version of those meetings has become such an embarrassment to the Administration that speculation arose that he would announce his resignation, possibly today. Instead, Clinton gave his aide a boost. "Altman knows there will be a steadily increasing drumbeat calling for his resignation," says TIME's Washington correspondent Suneel Ratan. "He was just trying to deflate this."