Hours before Newt Gingrich was to begin his precedent-setting prime time address, President Clinton hit the stump toremind America that the chief executive still has a role in government. "I was not elected president to pile up a stack of vetoes -- I was elected president to change the direction of America," Clinton told the American Society of Newspaper Editors in Dallas. He warned that the GOP had better modify its "Contract With America" proposals if they were to become law. So far, he said, he is inclined to support only the line-item veto and a $16 billion spending cuts package that the Senate passed Thursday night. Senate Minority Leader Richard Gephardt, chosen to respond to Gingrich's speech Friday, added his own pre-emptive strike: "The Republicans will try to impress us with the sheer volume of legislation they've passed, largely in one house of Congress -- as if it's the quantity, not the quality, of legislation that matters," Gephardt said.