The legislation, pushed through Congress by Lyndon Johnson in 1965, resulted in large part from a civil-rights campaign that culminated with state troopers beating marchers on Alabama’s Edmund Pettus Bridge. But it was driven, more fundamentally, by discriminatory practices that had endured for decades in the South.

The act eliminated literacy tests, “good moral character” requirements and other stratagems used to deny blacks the vote. Jurisdictions that had required such tests (and in which fewer than 50 percent of voting-age residents were registered) were placed under special scrutiny. Such jurisdictions, almost all of which were in the Deep South, were barred from changing voting rules or procedures without Justice Department “preclearance.” Some localities were forced to reconfigure district lines or to discontinue at-large elections.

The provisions allowing for federal monitoring were set to expire in 1970. But civil-rights advocates repeatedly succeeded (in 1970, 1975 and 1982) in having them extended. In the heat of one such battle in 1981 Vernon Jordan Jr., then president of the National Urban League and now a key Clinton adviser, declared: “I do not trust white people in the South with my rights.” It was not only Southerners who were not trusted. As the law was extended, it was also broadened-to a point that many felt went far afield of its original intent. It came to encompass “language minorities” and to apply to every state in the country.

Larger argument: The Justice Department now processes more than 17,000 preclearance requests a year, and voting-rights cases are in constant litigation. Two years ago the Supreme Court was asked to intervene when two counties in Alabama stripped county commissioners of much of their power after blacks were elected to the posts. In refusing to do so, Justice Anthony Kennedy’s majority opinion declared, “The Voting Rights Act is not an all purpose antidiscrimination statute.” John Stevens dissented, arguing that the court had previously deemed the law applicable where white majorities had conspired to disenfranchise blacks.

The disagreement mirrors a larger argument outside the court, pitting those who believe the law has strayed from its original purpose against those who believe that it has evolved appropriately in response to ever more devious efforts to discriminate. The argument is (as Jordan implied) largely about faith in the good intentions of one’s fellow Americans and also about whether Voting Rights Act enforcement should focus primarily on process or on results.

In her now famous Virginia Law Review article, Lani Guinier sided with those advocating a focus on results. She suggested cumulative voting-which provides all voters with as many votes as there are candidates and with the right to distribute those votes as they wish-as a way of keeping an “advantaged majority” from exercising “disproportionate power.” She also floated the idea of a “minority veto.”

What she meant by that is unclear; but her backers quickly pointed out that cumulative voting is not a radical or untested notion. In at least 32 jurisdictions-in Alabama, Georgia, North Carolina and Texas-the Justice Department approved cumulative or “limited” (meaning that voters get fewer votes than there are candidates) voting procedures during the last seven years of the Reagan and Bush administrations.

An unpleasant reality: With a nod to the Federalist papers, Samuel Issacharoff, a law professor at the University of Texas, argued that Guinier’s suspicion of majority domination and her support for minority rights were positively “Madisonian.” Danya Cunningham, of the NAACP Legal Defense and Education Fund, says Guinier’s writings merely acknowledge an unpleasant reality: “People get in that booth . . . they close that curtain, and they can’t move their fingers to vote for the black candidate.”

In recognizing that “reality,” both Guinier and the Voting Rights Act assume the worst about many Americans. That assumption makes some people profoundly uncomfortable. Sharing it helped to torpedo Guinier’s appointment to the Justice Department. But it is an assumption that neither her own experience nor the history of the act can convincingly rebut.