Abigail Thernstrom has written this article, published at 23 Stanford Law and Policy Review 373 (2012).  From the conclusion:

At its inception, the Voting Rights Act stood on very firm constitu-tional ground; it was pure antidiscrimination legislation designed to en-force basic Fifteenth Amendment rights. A clear principle justified its original enactment: citizens should not be judged by the color of their skin when states determine eligibility to vote. That clarity could not be sustained over time. As a result, more than four decades later, the law has be-come what Judge Bruce Selya has described as a “Serbonian bog.” The legal land looks solid but is, in fact, a quagmire, into which “plaintiffs and defendants, pundits and policymakers, judges and justices” have sunk.
In part the problem is the difficulty that “plaintiffs and defendants, pundits and policymakers, judges and justices” are having in finding their footing in a racial context so very different than that in which the statute had been enforced for most of its life. In following its own recently issued guidelines, the Justice Department may not soon start down untraveled roads, recognizing the waning of American racism. But administrations come and go, new people take charge of civil rights enforcement at the DOJ, new judges are appointed, and the racial zeitgeist continues to change. Today’s interpretation of the language of the guidelines is not likely to remain the definitive understanding of the demands of preclearance. Section 5 is set to expire in 2031; long before that date, the “Procedures for the Attorney General’s Administration of section five,” most recently issued in April 2011, will surely be altered in ways we cannot yet foresee. We know only this: the American racial landscape is fluid, and the law does respond to change.