Dilutive electoral devices such as at-large election systems and racial gerry-mandering have been challenged on at least two separate grounds. First, plaintiffs have cited constitutional issues, alleging that such devices violate the Equal Protection Clause of the Fourteenth Amendment and the guarantee in the Fifteenth Amendment that the right to vote shall not be denied on racial grounds. Second, and more recently, plaintiffs have relied on the Voting Rights Act. Especially since 1982, plaintiffs have argued that certain practices violate Section 2 of the act; for jurisdictions captured by the trigger provision of Section 4, Section 5 offers another alternative.

Section 5 cases were especially important after the 1970s round of redistricting because they could be brought against those jurisdictions considered the worst offenders and because the burden of proof rests with the jurisdiction attempting to alter the electoral practice or procedure. These cases significantly reduced the use of multimember districts in southern state legislatures (Grofman and Handley, 1991), and they remain, according to one civil rights lawyer, the “first line of defense” in the covered areas. Nonetheless, the applicability of Section 5 to only covered jurisdictions and to only changes in electoral practices is a severe limitation. Consequently, cases involving constitutional arguments were also brought throughout the 1970s and early 1980s. In 1982 the Voting Rights Act was again extended, and in the process important amendments were made to Section 2; most of the litigation since then has been based on that revision. Lower courts began interpreting the revised Section 2 immediately after it was approved, and eventually, in June 1986, the Supreme Court decided Thornburg v. Gingles, the current authoritative legal interpretation for most vote dilution cases.