With this year's elections fast drawing near, there are still several cases working their way through the courts on the validity of the new lines drawn by state legislatures. This past Monday, the Supreme Court issued a uananimous per curiam opinion in a case out of West Virginia (its second resdistricting opinion of the term) to draw the 2011-12 Term to a close.
The issue in Monday's decision was the impact of modern software on the rules governing judicial review of the new districts. The impact of this technology is slightly overstated as it was always possible to move individual census blocks to make districts more equal, but modern redistricting software makes it easy to draw very different maps and quickly get the total population of the districts in each of the maps. The Supreme Court's bottom line was that this new technology did not alter the rules for review. As such, while West Virginia could have drawn more equal distircts, the small deviation (less than 5.000 for districts of approximatly 700,000 individuals) was minor enough that the lower court should not have invalidated the districts in light of the reasons given by West Virginia for that deviation.
After Monday's decision (and the decision earlier in the term on the Texas court-drawn interim lines), the rules seem to be as follows:
1) A 5% difference in population between the smallest and largest district remains the absolute line at which the districts are automatically unconstituional. A smaller gap will require the state to provide a reason for the differences.
2) This reason does not have to be particular substantial. Instead, the courts will effectively defer to the legislative priorities including incumbent protection, minimizing changes from current lines, respecting existing political subdivisions (county lines, city limits, precinct lines, partisan advantage, etc.).
3) The one issue that will get some closer scrutiny is minority voting power. On the one hand, when there is a clear concentration of minority voters (large enough to comprise a substantial part of a district), attempts to dilute that vote will violate the Voting Rights Act. On the other hand, when there is not such a clear concemtration, drawing weird lines to connect two separate pockets with high minority population will violate the Equal Protection Clause.
4) Even when there is a finding of a Voting Rights Act problem (or any other illegality), any interim court-drawn lines should respect the priorities set by the legislature in the invalid districting map and should make only those alterations necessary to remedy the violation.
The big issue to be addressed later this term (probably) will be whether Southern states will still be required to pre-clear their new lines (in a Washington Court under the tougher Section 5 standards -- allowing lines to be invalidated if they represent a step backwards from previous lines). If pre-clearance is set aside, those seeking racially-fair lines in the South will be required to prove their case (in a local federal court) under the more lenient Section 2 standards (showing dilution of the voting power of racial minorities).