Mark Posner has written a very important White Paper, The Politicization of Justice Department Decisionmaking Under Section 5 of the Voting Rights Act: Is it a Problem and What Should Congress Do?. ACSblog describes it as follows:

The Constitution in the 21st Century Project Distributes White Paper on “The Politicization of Justice Department Decisionmaking Under Section 5 of the Voting Rights Act”
ACS is pleased to distribute an analysis by Mark A. Posner, examining recent administration by the Justice Department of Section 5 of the Voting Rights Act. Mr. Posner served as an attorney in the Civil Rights Division of the United States Department of Justice from 1980 to 2003, and assisted in supervising the Division’s reviews of Section 5 preclearance submissions from the mid-1980s to 1995. He currently serves as Adjunct Professor of Law at American University’s Washington College of Law and the University of Maryland School of Law.
Over the next year, Congress is expected to decide whether to renew Section 5 of the Voting Rights Act, one of the most effective civil rights protections ever enacted. Section 5, which will expire in August 2007 unless renewed, requires particular states and localities to obtain federal approval (“preclearance”) whenever they enact or seek to administer a change in any aspect of their election law or procedure. Recent reports suggest that some significant precelarance decisions have been driven by partisan political interests, rather than good faith application of the law to the facts. In his white paper, “The Politicization of Justice Department Decisionmaking Under Section 5 of the Voting Rights Act: Is it a Problem and What Should Congress Do?,” Mark Posner takes a hard look at the politicization question and ways Congress can address this concern in renewing Section 5 of the Voting Rights Acts.