Wesberry v. Sanders
One Person, One Vote
The concept that each individual's vote will carry the same weight as another was established by the U.S. Constitution, and was reiterated in Baker v. Carr (1962) and Wesberry v. Sanders (1964). Historically, the American colonists had disagreed with England's imposition of taxation without actual representation. They argued that "virtual" representation of the colonists in Parliament was inadequate.
In framing the Constitution, the authors intended to avoid the problem of representation in elections for Congress. In order to provide a balance between conflicting needs of the more populated states versus the less so, they devised a system whereby both population densities were addressed. In the Senate, each state would have two senators. In the House, the representation would be based upon population in the state. Realizing potential growth and shifting populations, a provision was made to reapportion the number of representatives of each state based upon a national census to be conducted every ten years.
Boundaries in voting districts may be redrawn allowing for movement of populations. This continual reassessment of populations provides the basis for the argument that each person's vote in congressional elections carries similar weight to any one else's vote.