Final answer:
The 'one person, one vote' principle means that each voter's ballot is equal in an election, as established in Reynolds v. Sims. This requires electoral districts to contain similar numbers of voters to ensure fair representation.
Step-by-step explanation:
The principle of one person, one vote as used by the Supreme Court in the reapportionment decisions means that every voter's ballot should carry the same weight. This concept was affirmed in the landmark case Reynolds v. Sims (1964), which determined that electoral districts must be drawn so that they each contain roughly the same number of voters. This ensures that representation is equal across districts and that no individual or group has disproportionate power in an election.
Following the ruling, states were required to adjust their electoral maps to achieve equal populations in districts, and subsequent redistricting efforts have been focused on maintaining electoral balance. The principle enforces the idea that every citizen's voice should have an equal impact on the outcome of elections. As such, gerrymandering practices were scrutinized to ensure fair representation, barring districts drawn intentionally to favor a party or incumbent.