There are three major issues in the Texas redistricting case: voting rights, partisan gerrymandering, and mid-decade redistricting. I shall comment on the latter two.
In Davis v. Bandemer, 478 U.S. 109 (1986), the Supreme Court held that constitutional challenges to partisan gerrymanders are justiciable but that gerrymanders do not violate the Constitution except under extraordinary (nearly impossible) circumstances. In Vieth v. Jubelirer, 124 S.Ct. 1769 (2004), a plurality of four justices would have overruled Bandemer because of an ill-founded conclusion that Bandemer failed to establish manageable standards. Four justices dissented. The pivotal vote was cast by Justice Kennedy. In a remarkably irresponsible decision, Kennedy declined to join the plurality's finding that no manageable standards exist, but adamantly refused to suggest what the proper standards might be. As I say in a commentary on Vieth in a forthcoming symposium in the Cornell Journal of Law and Public Policy, Kennedy's opinion is like a black hole-it not only fails to shed light to guide lower courts, it affirmatively acts to prevent light from escaping.
Now that the Texas case is back in the Supreme Court following a well-crafted lower court opinion denying relief, the first noteworthy fact is that two members of the Vieth plurality, Chief Justice Rehnquist and Justice O'Connor, are no longer on the Court. It seems likely but by no means certain that their replacements, Chief Justice Roberts and Justice Alito, will take positions similar to theirs. In that case, Kennedy will again become the pivotal vote. His performance in Vieth was dismal enough, and he may be reluctant to repeat it. I suspect he will grab at an opportunity to avoid deciding the partisan gerrymandering question if he can. If not, he may want to crawl out of the black hole (the simile is getting strained here!). In which direction? That's hard to say, but the most likely explanation for his posture in Vieth is that he subscribes to the anti-gerrymandering mythology and does not want to commit to keeping his hands off redistricting.
Some of the other commentators here discuss the perception of partisanship that may or may not ensue depending on how the Court rules. I agree with Professor Smith that serious criticism for partisanship is not likely to follow from the Texas case itself. But if the Court calls for intervention on political grounds, it commits the federal judiciary to an inherently partisan activity for the indefinite future. There are no compelling public interest principles, much less constitutional principles, governing the politics of redistricting, other than that plans should be the outcome of free negotiation and competition.
Space does not permit elaboration here on the many additional reasons why judicial intervention into partisan gerrymandering is a bad idea. Some of them are developed in Lowenstein & Steinberg, "The Quest for Legislative Districting in the Public Interest: Elusive or Illusory?" 33 UCLA Law Review 1(1985); the above-mentioned forthcoming article on Vieth; and the White Paper prepared by the No on 77 Committee in last year's California campaign on Governor Schwarzenegger's redistricting proposal. (I chaired that committee but did not write the White Paper.)
Mid-decade redistricting is a bad idea. One reason I believe the crusade against partisan gerrymandering is based on mythology is that it greatly exaggerates the potency of districting as a partisan tool. If districting plans could be updated every two years, the crusade would still be exaggerating the dangers but not nearly as much. Furthermore, there is some benefit in stable districts and the once-a-decade cycle represents a good balance between stability and the need to keep up with shifting population.
Some states prohibit redistricting more than once per decade in their constitutions. In California, our Supreme Court read such a restriction into the constitution early in the twentieth century and reaffirmed that position in Assembly v. Deukmejian, 180 Cal. Rptr. 297 (1982). The California rule prohibits more than one legislatively-drawn plan per decade. What Texas did would not violate the California rule, because the mid-decade plan replaced a judicially-drawn plan. Whether the rule should prohibit mid-decade replacement of judicially-drawn plans is fairly debatable and probably not very important. But a once-a-decade rule, in whichever form, is good policy.
That does not mean mid-decade districting is unconstitutional. I agree with the thrust of Professor Smith's commentary here, that the Court should be applying the Constitution, not acting as a roving election law reform commission. The Constitution leaves districting procedures to the states, subject to congressional oversight in the case of districts for the House of Representatives. States that do not already have them should add mid-decade prohibitions to their constitutions. Congress should enact a ban on mid-decade changes in House districts.