Collective name of six cases argued 13 November 1963 and decided 15 June 1964: involving Alabama—Reynolds v. Sims, 377 U.S. 633 (1964), decided by vote of 8 to 1, Warren for the Court, Harlan in dissent; involving New York—WMCA v. Lomenzo, 377 U.S. 633 (1964), decided by vote of 6 to 3, Clark and Stewart joining Harlan in dissent; involving Maryland—Maryland Committee for Fair Representation v. Taws, 377 U.S. 656 (1964), decided by vote of 7 to 2, Clark concurring, Harlan in dissent, Stewart, refusing either to affirm or reverse, would nonetheless vacate the judgment of the court; involving Virginia—Davis v. Mann, 377 U.S. 656 (1964), decided by vote of 8 to 1, Warren for the Court, Clark and Stewart concurring, Harlan in dissent; involving Delaware—Roman v. Sincock, 377 U.S. 695 (1964), decided by vote of 8 to 1, Warren for the Court, Clark and Stewart concurring, Harlan in dissent; and involving Colorado—Lucas v. Forty-Fourth General Assembly of Colorado, 377 U.S. 713 (1964), decided by vote of 6 to 3, Warren for the Court, Harlan, Clark, and Stewart in dissent.
These cases effectively declared the apportionment of every state legislature unconstitutional.
They were prompted by Baker v. Carr (1962), which opened federal courts to cases in which state legislatures were challenged for failing to provide equitable legislative districts and thereby depriving citizens of equal protection of the laws. Earlier in its 1963 term, in Wesberry v. Sanders (1964) the Supreme Court had extended the requirement of population equality (i.e., that districts must be as nearly equal as is practicable) to electoral districts for seats in the House of Representatives; that decision had been based on its reading of Article 1, section 2.
Chief Justice Earl Warren's opinion in Reynolds v. Sims, which along with Lucas was the leading case, reemphasized the “one man, one vote” principle announced the year before in Gray v. Sanders (1963), a case setting aside Georgia's gubernatorial county unit system. “Legislators represent people,” wrote Warren “not trees or acres. Legislators are elected by voters, not farms or cities or economic interests” (p. 562). The Court also rejected the “federal analogy” argument that the states, like Congress, could base only one house on population. As the Court repeatedly stated throughout the opinion, “The Equal Protection Clause requires that the seats in both Houses of a bicameral state legislature must be apportioned on a population basis.” Each state legislative district should be “as nearly of equal population as is practicable,” as based on the most recent decennial census (p. 577). The Court, however, noted, “Somewhat more flexibility may … be constitutionally permissible with respect to state legislative apportionment than in congressional districting” (p. 578).
Warren, responding to Justice John M. Harlan's dissent and to the earlier warnings of Justice Felix Frankfurter, commented: “We are cautioned about the dangers of entering into political thickets and mathematical quagmires. Our answer is this: a denial of constitutional protected rights demands judicial protection” (p. 567).
The other cases applied the doctrines of Reynolds to the facts of the involved states, except in Lucas v. Forty-Fourth General Assembly of Colorado, where the Court held that the fact that the Colorado apportionment plan had been incorporated into the state's Constitution via the initiative process did not protect it from federal constitutional challenge.