Reynolds v. Sims
Significance: The Supreme Court clearly established the one person, one vote principle for all legislative districting except the U.S. Senate.
Many states had state senates apportioned on a geographical basis, providing an equal number of senators to each county no matter how widely the population varied, just as the U.S. Senate was apportioned. The Supreme Court, by an 8-1 vote, ruled that both houses of a state legislature had to be apportioned according to the one person, one vote principle that the Court laid down in Gray v. Sanders (1963). However, the Court did not accept that counties stood in relation to their state as the states did in relation to the nation and allowed an exception to the one person, one vote principle in apportionment for the U.S. Senate. This decision led to widespread protests and an unsuccessful attempt to overturn the decision through constitutional amendment.