In the 1963 case Lucas et al. v. Forty-Fourth General Assembly of Colorado et al., the U.S. Supreme Court ruled that a redistricting plan for the state of Colorado violated the Equal Protection Clause of the Fourteenth Amendment because it diluted urban voters' influence in favor of rural areas, creating an imbalance in representation. The court found that while states have some leeway to draw district lines based on factors other than population, such as maintaining political subdivisions or geographic considerations, these cannot result in substantial inequality among citizens' voting power within a state's legislative bodies. This ruling reinforced and clarified principles established by earlier cases like Baker v Carr (1962), which recognized federal courts' authority to intervene in apportionment issues and affirmed "one person, one vote" as a constitutional standard.

In the dissenting opinion for Lucas v. Forty-Fourth General Assembly of Colorado, Justice Harlan argued that the court majority had overstepped its authority by intervening in a matter he believed should be left to state legislatures and voters. He contended that there was no constitutional requirement for both houses of a bicameral legislature to reflect population distribution perfectly, as long as each citizen's vote carried equal weight within their respective legislative body. Furthermore, he asserted that it was not the Court's role to dictate how states should structure their governments or determine what constitutes "fair" representation. Instead, these decisions should be made through democratic processes at the state level.