PEOPLE familiar with the flamboyant career of Edwin Edwards may find it incongruous that the former Louisiana governor is a vehicle for a protest vote against political chicanery. Mr. Edwards, with his Mardi Gras ways and populist rhetoric, has often been associated with a Louisiana political style that traces back to Huey Long. But as a political prescription for Louisiana, "let the good times roll" is better than "roll back the clock."And there are many indications that a victory for David Duke in the Bayou State's gubernatorial runoff Saturday would indeed roll back the clock on the great advances Louisiana, the South, and the nation have made in a generation toward harmonious race relations and equal opportunity for all. Mr. Duke is a former adherent of the American Nazi Party who humbugs the Holocaust, a former grand wizard of the Ku Klux Klan, and the founder of a white-supremacy group that publishes racist and anti-Semitic literature. Though only 41, Duke has been affiliated for nearly 30 years with hate groups on the bigoted fringe of American politics. Duke has tried to disavow his "youthful indiscretions," but he has not been convincing. His recent claims to have been born again as a Christian seem transparently political. And even if he truly aspires to religious redemption, he needs to live that quest for a matter of years, not months. Fortunately, the battle against intolerance in America has advanced too far for a David Duke to reverse it single-handedly, even in his own state. But his win could signal other office seekers that the economic and social concerns of America's white middle class can be tapped into through a politics of resentment and coded appeals to bigotry. Politicians need to heed middle-class worries about the economy, health care, crime, and their children's schools. But these problems must be tackled honestly and constructively, not by creating scapegoats among racial and ethnic minorities. That's a message Louisiana voters should deliver to David Duke and all of America.