THE subject of racial preferences in hiring arouses a certain segment of voters in the United States. This was clear during David Duke's run for governor of Louisiana, when his supporters cited government policies favoring blacks and other minorities as a reason for backing Mr. Duke. Only he, they said, was willing to make an issue of this.Not true. There are people in the Bush administration who have been only too happy to trumpet racial preferences, or "hiring quotas," to use the catch-all term. So happy, in fact, that they tried to revive the subject after the passage of the civil rights bill had supposedly quieted things down. Mr. Bush wisely overruled his aides' plans to scrap the federal rules that have guided civil-rights enforcement and encouraged affirmative action for the past two decades. Affirmative action, designed to help minority citizens over hurdles raised by past discrimination, is sometimes loosely equated with "reverse discriminaton." It has unquestionably brought blacks and Hispanics into public-sector jobs historically closed to them. It has given minority-owned businesses a boost by requiring access to government contracts. In the course of these changes, have thousands of other Americans been unfairly displaced, as Duke backers and others assert? Individual cases of unfairness have no doubt occurred, and they ought to be guarded against. But the charge of widespread injustice is a distortion. Affirmative action has had its greatest impact in municipal employment, but such jobs make up only a tiny fraction of the employment in any given metropolitan area - around 5 percent, for example, in New York City. Blacks in the US continue to have a jobless rate twice that of whites. Cutbacks in public payrolls during the recession have hit blacks, who are likely to have been the most recently hired, hard. Policies that help bring all Americans into the economic mainstream are still needed. The legacy of discrimination is far from erased. Economic hard times make the subject of racial preferences politically potent. Responsible politicians will resist the temptation to take it up.