A poll released Monday by the D.C.-based firm Hahn & Associates revealed that 71 percent of Americans approve of President Clinton's current approval rating of 63 percent. According to the poll, just 11 percent of Americans believe Clinton's approval rating should be 'significantly lower,' while 18 percent believe it should be 'much higher.' 'This poll is a clear public mandate for the president, as a great majority of Americans strongly support his current level of support,' White House press secretary Mike McCurry said. The 71 percent represents Clinton's highest approval-rating approval rating since taking office. 