In the case of Mahan v. Howell, the Supreme Court ruled on a dispute regarding electoral districting in Virginia. The plaintiffs argued that the state's reapportionment plan violated the Equal Protection Clause of the Fourteenth Amendment due to population variances among districts. The defendants contended that these discrepancies were justified by maintaining political boundaries and preserving communities' interests. In a 5-4 decision, it was held that minor deviations from mathematical equality among state legislative districts did not make them unconstitutional per se as long as they were based on legitimate considerations incident to effectuation of rational state policy. This ruling clarified previous decisions about redistricting and established more flexible standards for evaluating constitutionality under equal protection principles.

In the dissenting opinion for Mahan v. Howell, Justice Brennan disagreed with the majority's ruling that Virginia's reapportionment plan was constitutional despite its deviation from perfect population equality among districts. He argued that any deviation from strict population equality must be justified by a compelling state interest and believed that the majority had failed to apply this standard rigorously enough. In his view, maintaining political boundaries or preserving communities of interest were not sufficient reasons to allow significant deviations in district populations. Furthermore, he criticized the majority for failing to provide clear guidance on what level of population variance would be acceptable under their more lenient approach. This lack of clarity could lead states to draw districts with even larger disparities in future redistricting efforts, undermining equal representation.