You can read the brief (Paul Clement, counsel of record) here.  It makes statutory arguments the Court is likely to consider about the meaning of the Voting Rights Act’s section 5 preclearance provision and it raises the issue of section 5’s constitutionality:

This Court has been asked several times in recent years to reconsider the facial constitutionality of Section 5. See Northwest Austin Mun. Util. Dist. No. One v. Holder, 129 S.Ct. 2504, 2509 (2009); Shelby County v. Holder, No. 12-96; Nix v. Holder, No. 12-81. Those cases raise critically important issues about Section 5, but they do not directly illustrate the burdens of the preclearance process.

This case is different. It demonstrates the acute federalism costs when Section 5 is invoked to prevent a State from implementing changes to its electoral maps necessitated by population growth. The requirements of the Constitution and Section 2 ensure the absence of unconstitutional consideration of race. In contrast, the requirements of Section 5, especially as interpreted by the district court, virtually mandate an obsession with race and guarantee unprecedented intrusions into state sovereignty. The decision below clearly merits this Court’s review in its own right and would complement other Section 5 cases by showing the difficulties with the practical administration of the statute as reauthorized in 2006. The Court should note probable jurisdiction and set this case for oral argument this Term so that Texas can implement its legislatively enacted plans for the next electoral cycle.