I was at the Supreme Court for oral argument in Evenwel v. Abbott, the case asking whether states have to draw legislative districts that equalize voters or people. (For more background, see here and Cato's brief, and the argument transcript.)
I don't have much to add to the excellent analysis of our own Andrew Grossman, other than to highlight that it looks like the ruling will come down to the votes of Chief Justice John Roberts and Justice Anthony Kennedy. Justice Samuel Alito seems to be the only safe vote for the challengers, though one can infer from their pasts that Justices Clarence Thomas -- who dissented 15 years ago from the Court's decision not to take a previous case raising this issue but maintained his characteristic silence -- and Antonin Scalia -- who was (very) uncharacteristically silent -- are also on that side. The four members of the so-called liberal bloc, meanwhile, were unflinching in their attack on the challengers' position as threatening representational interests and also being impractical.
Justice Kennedy seemed to want to have it both ways, asking Texas Solicitor General Scott Keller (a friend of mine), "Why can't you use both [population equality and voter equality]?" That approach may well appeal to the chief justice, who could, in the alternative, simply defer to the states (which is Texas's position, while the United States insists that total population must be the measure used).
Indeed, it's possible that we end up with a 3-2-4 split, in which case the Kennedy/Roberts position would set the controlling precedent and we would still see a change in how at least some states draw district lines without affecting the more significant nationwide standard that the challengers request.
Such a split-the-baby decision, while perhaps emblematic of the Roberts Court, would be constitutionally unsatisfying. As I write in my new USA Today oped:
The Supreme Court must thus intervene again, to maintain voter equality by specifying that “one person, one vote” demands an equalization of voters rather than population.
Otherwise, you end up with the scenario we see in Texas. Depending on where you live in the Lone Star State, you might be one of 383,000 people who choose a state senator, or one of 611,000. Indeed, the legislature could’ve drawn 31 districts of equal population where 30 have one voter each and the 31st all the other voters.
That can’t be right. If “one person, one vote” means anything, it’s that we can’t weigh some people’s votes more than others’.