I have a piece at the Online Library of Law and Liberty today on Evenwel v. Abbott, a challenge to Texas's state legislative redistricting system that draws districts on the basis of total population instead of voters. It concludes:

Texas, along with the other 49 states, has remained free to adopt one of several theories of representative government within the confines of Reynolds v. Sims. But Evenwel threatens not only to deprive the states of their authority to do so, but also to impose a standard that is squarely at odds with the structural design of the Constitution: representative government includes representation of all persons, not simply voters.