In a rare meeting with reporters in early July 1968, Chief Justice Earl Warren answered readily when asked which of the Court’s decisions in his momentous years on the Supreme Court were most important. The series of rulings, he said, that created the constitutional idea of “one person, one vote.” That is a basic theory of democratic representation: no individual’s vote may be weighted more heavily than any other’s. Election districts, for Congress and state legislatures, must be drawn as close to equal in population as can practically be done. The clearest expression of that idea came in the 1964 decision in Reynolds v. Sims. Now, a half-century later, the Court has assigned itself the task of deciding — remarkably, for the first time — how to get to that goal. What, it will answer in one case, population measure should be used: total people in a district, total citizens, total citizens of voting age, total numbers of registered voters? And, in a second case, the Court will answer whether it violates the equality principle if districts are drawn in a way that favors one party’s candidates. Both cases involve cross-currents of political theory, and both have the potential to directly change election outcomes and the election fortunes of the two major political parties. There is considerable complexity here, so let’s try to make this simple.
The “overriding objective” in pursuing the “one person, one vote” mandate, the Court said in 1964, “must be substantial equality of population among the various districts so that the vote of a citizen is approximately equal in weight to that of any other citizen in the state.” It would say later that absolute mathematical equality is not required, and that some departure from equality is permitted to serve other legitimate state policies or interests.
Still, the starting point of the exercise is population — so far, population without a constitutionally binding definition. If practice were controlling, because this is how it’s done in most states, the starting point would be a state’s total population divided by the number of election districts, for state legislatures or for a state’s delegation to the U.S. House of Representatives. The usual measure of whether the equality principle has been denied is to compare the numbers gap (technically, the “maximum deviation”) between the most-populated district and the least-populated district.