This topic is monitored by Moritz Law Professor Steven F. Huefner
The Current Status of One-Person-One-Vote: An Overview
The constitutional principle of one-person-one-vote has been enforced differently with respect to congressional districts than with districting for state legislatures (or other state or local elections). For congressional districts, which elect members of the U.S. House of Representatives, the Supreme Court has required strict compliance with one-person-one-vote, saying that any deviation from population equality must be justified by a legitimate reason. See Karcher v. Daggett, 462 U.S. 725 (1983). By contrast, for state legislatures, it had been thought that the Supreme Court would tolerate, essentially without need for justification, deviations of up to 10% from strict population equality. In other words, if the largest district has 105,000 residents, while the smallest has 95,000, and the average population of all districts is 100,000, this gap of 10,000 from largest to smallest would not be enough to invalidate a districting plan.
A new ruling by the U.S. Supreme Court, in a case from Georgia, Cox v. Larios, No. 03-1413 (June 30, 2004), casts doubt on that settled understanding. That case involved a population deviation of just under 10% — 9.98%, to be exact — but the Supreme Court affirmed the district court's decision that it was invalid because it was designed to maximize inner-city voting power and minimize suburban voting power, in large part because the Democrats in Georgia controlled the districting process and they saw the inner-city as a source of strength and suburbia as a place of weakness. Although the Supreme Court's affirmance was summary, without an opinion and without benefit of oral argument, this decision is likely to be viewed as a precedent with significant implications for how redistricting proceeds in other states. before Larios, the Supreme Court — by a deeply divided 5-to-4 vote — rejected the idea that a partisan gerrymander could be proved to be unconstitutional in a case where each district has the same number of people. In that case, Vieth v. Jubilerer, 124 S.Ct. 1759 (April 28, 2004), the argument had been made that partisan gerrymandering was a separate constitutional problem: even if each district is equal in population, district lines can be drawn in a way to frustrate the democratic will of the electorate. (Specifically, gerrymanders work to keep a political party in control of the state legislature even after the party has lost support of the majority of voters statewide, because the gerrymander gives this controlling party a small but decisive advantage in a majority of districts, while packing supporters of the opposing political party into the remaining districts, where their overwhelming voting strength does no good in achieving majority party status in the legislature.) By rejecting the constitutional challenge in Vieth, while sustaining the population inequality claim in Larios, the Court has forced litigation over districting plans to focus on population deviations. Even when the argument is that the population deviations are unjustified because the districting has been done for partisan reasons, the litigants must show the population deviations first and address the issue of partisanship only after this threshold showing.