In the case of Mandel, Governor of Maryland, et al. v. Bradley et al., 1976, the Supreme Court ruled on a dispute regarding redistricting in Maryland following the 1970 census. The appellants argued that their constitutional rights were violated because they were not given an equal vote due to population variances among legislative districts. However, the court upheld lower courts' rulings that these discrepancies did not violate "equal protection" principles as long as there was no systematic discrimination against certain groups or individuals and if reasonable efforts had been made to achieve population equality across districts. This decision emphasized that while absolute equality is desirable in district populations for fair representation, minor deviations are permissible when justified by legitimate state interests such as maintaining political subdivisions or geographic boundaries.

In the dissenting opinion for Mandel v. Bradley, Justice Brennan disagreed with the majority's decision to uphold Maryland's multi-member district electoral system. He argued that this system was unconstitutional as it diluted minority voting power and violated equal protection principles under the Fourteenth Amendment. Brennan contended that a single-member district would provide a more equitable representation of voters' interests, particularly those from racial or political minorities who were often marginalized in multi-member districts due to their inability to secure enough votes for representation. He also criticized the Court’s reliance on statistical evidence rather than considering whether there was an actual discriminatory effect on minority groups’ ability to participate in elections effectively.