In the case of Swann et al. v. Adams, Secretary of State of Florida, et al., 1966, the U.S Supreme Court ruled that a state's legislative districts must be roughly equal in population to ensure fair representation for all citizens under the Equal Protection Clause of the Fourteenth Amendment. The appellants were residents and qualified voters from Dade County who challenged Florida’s apportionment plan on grounds that it diluted their votes by creating unequal populations among various senatorial and representative districts across counties. They argued this violated their constitutional right to equal protection under laws as some legislators represented significantly more constituents than others did due to uneven districting practices. The court agreed with them stating that "as nearly as is practicable one man's vote in a congressional election is to be worth as much as another's." This ruling established an important precedent known as “one person, one vote,” which has been used since then to challenge gerrymandering or unfair redistricting practices.

In the dissenting opinion for Swann et al. v. Adams, Justice Harlan argued that the court was overstepping its boundaries by involving itself in political matters such as legislative apportionment and redistricting, which he believed should be left to state legislatures and Congress. He contended that there were no judicially manageable standards for determining when a state's apportionment plan violated the Equal Protection Clause of the Fourteenth Amendment, making it inappropriate for courts to intervene in these cases. Furthermore, he expressed concern about potential consequences of this decision on federalism and separation of powers principles.