What 1964 Supreme Court case established the 'one person, one vote' principle, ruling that state legislative districts must be roughly equal in population?

• A Baker v. Carr
• B Gomillion v. Lightfoot
• C Wesberry v. Sanders
• D Reynolds v. Sims ✓

Reynolds v. Sims applied the Equal Protection Clause to require that both houses of state legislatures be apportioned based on population, ending the practice of some districts having many times the population of others.