Nate Persily, Charles Stewart III, and Steve Ansolabehere have written an important new paper [updated], which I have now posted.  The paper comes just in time for argument in the Shelby County case.  Here is the introduction (minus the footnotes):

Three years ago, when the Supreme Court last considered the constitutionality of the coverage formula of Section 5 of the Voting Rights Act, we submitted an amicus brief on behalf of neither party analyzing the relevance to the case of voting patterns in the 2008 election.1 In particular, the brief and a subsequent Harvard Law Review article that expanded upon it,2 highlighted relative rates of racially polarized voting in the covered and noncovered jurisdictions to demonstrate where racial polarization had increased over time. Although some states had improved and others worsened in the gap in candidate preferences between racial groups, the brief and article concluded that, contrary to much conventional wisdom, racial polarization had actually increased in the 2008 election, especially in the areas covered by section 5 of the VRA.

We find ourselves in much the same position now as we did three years ago. We also find ourselves coming to the same conclusions, which have become, if anything, more strongly supported by recent data. Voting in the covered jurisdictions has become even more polarized over the last four years, as the gap between whites and racial minorities has continued to grow. This is due both to a decline among whites and an increase among minorities in supporting President Obama’s reelection. This gap is not the result of mere partisanship, for even when controlling for partisan identification, race is a statistically significant predictor of vote choice, especially in the covered states.
Moreso now than four years ago, both sides in the VRA debate look to the 2012 election to support their case. Critics of the VRA point to the reelection of the nation’s first African American president, amidst record rates of minority voter turnout, as evidence of how “times have changed” since 1965. The “strong medicine” of the VRA is no longer needed in the South,3 they argue, because the historic barriers to minority participation and office holding have largely vanished. For supporters of the VRA, the history since 1965 and the 1982 reauthorization demonstrate the continuing danger to minority voting rights in the covered jurisdictions. They point also to this past election as confirming Congress’s suspicions in the reauthorization process as new obstacles to voting, such as photo identification laws and restrictions on early voting, were more prevalent in the covered states. In the run up to the 2012 election, section 5 proved it had bite, as photo ID and other laws were prevented from going into effect by the DOJ or the District Court in Texas, South Carolina, and Florida, and Texas’s congressional redistricting plan was found to be intentionally discriminatory.
These contrasting views of the relevance of the 2012 election may very well provide the media frame for the debate over section 5 in the current challenge to the VRA in Shelby County v. Holder. Of course, the contending narratives of – “look how far we’ve come” versus “see how much voting discrimination persists” – are usually not the stuff of constitutional arguments. Moreover, the results of a highly salient and well-funded presidential election may seem beside the point for the constitutionality of a law that has its greatest effect in the context of local, below-the-radar, election law changes.
All involved in the debate over the VRA must admit, however, that we do not know exactly what the world will look like if section 5 is struck down. Of course, the South would not revert back to Jim Crow days: politics has evolved beyond the days of threatened lynchings for the exercise of the franchise. But the many examples in the legislative record of voting rights violations prevented by the VRA hint at what might happen if the covered jurisdictions were otherwise unconstrained. Even if Jim Crow will not return, the familiar regional pattern of discrimination might, as new stratagems replace old ones with minority voters becoming collateral damage in increasingly vicious partisan fights.
The litigants in the Shelby County case disagree over the applicable constitutional test and the necessary evidentiary showing for upholding the VRA. In particular, the challengers assert that Congress needed to distinguish the covered from the noncovered jurisdictions, in order to demonstrate that the coverage formula captures the areas of the country (and only those areas) that pose the greatest threat to minority voting rights. From their perspective, the coverage formula can only be “congruent and proportional”4 (and therefore constitutional) if it is precisely tailored to capture only “guilty” jurisdictions and no “innocent” ones.
Although defenders of the VRA point to higher rates of successful section 2 VRA cases as one example of where the covered states have distinguished themselves as voting rights iolators, they also maintain that Congress need only justify continued coverage by finding persistent dangers to voting rights in covered areas alone. The coverage formula, from its inception, has always been over and underinclusive of the jurisdictions of concern. Overinclusivity is addressed by the bailout provision, which allows “good” jurisdictions to escape coverage when they can demonstrate a clean voting rights record. So long as the coverage-formula-plus-bailout regime represents a rational attempt to address the problem of minority voting rights violations, defenders argue, the law is constitutional.
The challengers’ argument against the coverage formula would put Congress in an awkward position whenever justifying a geographically specific civil rights law. If the covered jurisdictions remain completely unchanged in their disrespect for minority voting rights, then the VRA is not working as promised. On the other hand, successful deterrence of voting rights violations in the covered states becomes evidence of its unconstitutionality if those jurisdictions become less distinct. In the oral argument in NAMUDNO, Chief Justice John Roberts described this problem as “the Elephant Whistle problem.” To summarize the allegory: A guy with a whistle around his neck walks into a bar. Another guy asks him, “why are you wearing a whistle around your neck?” “It’s to keep away elephants,” the first responds. “How do you know it’s working?” the second asks. “Do you see any elephants around here?”
If the Court takes the elephant whistle problem seriously, the challenge for defenders of the VRA is to find a metric that can hint at the danger of the VRA’s removal while simultaneously not suggesting it either has been ineffective or has outlived its usefulness. To some extent, the number of preclearance denials and DOJ requests for more information can do this by pointing at the types of laws that would have gone into effect but for the existence of the VRA. But even those data are incomplete because they cannot pick up the VRA’s deterrent effect – that is, the laws that were never proposed or passed because politicians knew they would not be allowed to go into effect. We should expect the number of laws denied preclearance to be small as compared to the number of laws that are never passed because of the VRA’s deterrent effect.