Dick Engstrom has written this article in Politics, Groups, and Identities.  Here is the abstract:

The preclearance provision of Section 5 of the Voting Rights Act was rendered ineffective by the United States Supreme Court in 2013 in Shelby County, AL v. Holder. This provision required federal review of changes in the election policies and practices of state and local governments with particularly bad histories of racial discrimination in their electoral processes. This essay identifies the crucial prophylactic role the provision played in preventing the implementation of vote denial and vote dilution practices in southern states. It provides an overview of the various reauthorizations of the provision, with particular attention to the latest in 2006, and a critical review of the Supreme Court’s response to it. Special attention is devoted to the social science evidence relied upon by Congress in that reauthorization and by the Court in its response to it.