“One man, one vote” is a slogan used to express an ideal of equal representation for all citizens. One man, one vote is also often expressed as one person, one vote.
In practice, the phrase has been used to argue for redistricting, especially to favor densely populated urban regions over less populated rural areas. One man one vote is closely associated with a series of decisions made by the Supreme Court in the 1960s.
One particular case, Reynolds v. Sims, dealt with the question of whether the state of Alabama should be required to redraw its district lines. The state’s district lines had not been changed since the census of 1900, when a far greater part of the state’s population was rural. Plaintiffs argued that the urban votes were being diluted and that each urban vote was, in effect, worth much less than each rural vote.
In a 1964 decision, the Supreme Court ruled that Alabama’s districting system did, in fact, violate the equal protection clause of the 14th amendment to the Constitution. Chief Justice Warren famously wrote in his decision that:
Legislators represent people, not trees or acres. Legislators are elected by voters, not farms or cities or economic interests. As long as ours is a representative form of government, and our legislatures are those instruments of government elected directly by and directly representative of the people, the right to elect legislators in a free and unimpaired fashion is a bedrock of our political system.