The partisan gerrymandering case argued this week in the Supreme Court presents one of the most important, difficult and intriguing legal questions of the last quarter-century.
The constitutional issue in the case, coming out of Wisconsin, is whether and when courts should invalidate redistricting plans that are designed to give a strong advantage to one political party. In extreme cases, such plans are an obvious violation of the Constitution. The problem is that it's not at all obvious how courts can police them.
To see why the constitutional violation is obvious, imagine a state where party X now has control of the state legislature, but where party Y has more voters -- say, a healthy margin of 2.3 million to 1.7 million voters. What can party X do to maintain its control in the future?
The simple answer is that its officials can use arithmetic and map-making skills to entrench themselves through redistricting.
For example, party X might create five districts, each with 800,000 people. Three of them might be designed so that its voters outnumber party Y's by 500,000 to 300,000. Two of them might be designed so that party Y's voters outnumber party X's, 700,000 to 100,000.
Voila! Party X is pretty well guaranteed to get 60 percent of the representatives -- even though it has just 42 percent of the voters. With a little luck, the party should be able to entrench itself for a very long time.
In this week's oral argument, most of the justices seemed to agree that in principle that's unconstitutional. As Justice Ruth Bader Ginsburg put it, "what becomes of the precious right to vote?"
Justice Anthony Kennedy asked about a state law explicitly stating that in designing districts, "the overriding concern is to have a maximum number of votes for party X or party Y." Such a law would, and should, be struck down in a heartbeat.
The problem of partisan gerrymandering has become worse than ever. Technology is allowing officials to obtain and to use extraordinarily sophisticated data about their citizens and how they are likely to vote. In a period of acute polarization, officials are in an increasingly good position to choose their voters, rather than the other way around.
That's essentially what happened in Wisconsin. The Wisconsin State Assembly, dominated by Republicans, engaged in a redistricting process specifically designed to ensure that Republicans would maintain a supermajority in the Assembly, even if Democrats got a majority of the statewide vote.
More particularly, they "packed" Democratic voters, by drawing district lines so that they were concentrated in specific districts. They also "cracked" Democratic voters, by splitting them up so that they were outnumbered by Republicans in other districts. The result? A large and likely durable advantage for Republicans.
In principle, that's tough to defend on constitutional grounds. But in 2004, four members of the court -- a plurality rather than a majority -- said that courts should never get involved in disputes about partisan gerrymandering.
Speaking for the four, Justice Antonin Scalia argued that there are "no judicially discernible and manageable standards for adjudicating" those disputes. In his view, it was impossible to produce a legal test that real-world judges could use to distinguish between permissible and impermissible gerrymandering.
Officials draw district lines for all sorts of reasons. How can judges possibly discern the intentions of those who produce district lines? And if the party that originally drew those lines ends up keeping its majority through subsequent elections, that doesn't prove anything untoward; after all, Democrats sometimes vote for Republicans, and vice versa. Political affiliation isn't the only factor that affects voting.
Justice Kennedy -- the crucial vote back in 2004, and very possibly now as well -- refused to join Justice Scalia's opinion. He agreed that no legal standard had yet been formulated. But he thought that in the future, a "limited and precise rationale" might found be "found to correct an established violation of the Constitution" in redistricting cases.
Much of Tuesday's oral argument focused on whether such a rationale could be found. Chief Justice John Roberts worried that it could not be -- and that if the Supreme Court gets in the business of evaluating partisan gerrymandering, it will have to take sides with either Democrats or Republicans, thus causing "very serious harm to the status and integrity of this Court in the eyes of the country."
Several of the justices focused on newly developed statistical tests, which ask whether both parties are equally able to turn popular support into legislative representation -- "partisan symmetry," as it is called. Social scientists have developed sophisticated methods for measuring partisan symmetry.
Chief Justice Roberts worried that those methods are "sociological gobbledygook." They aren't, but he's entirely right to ask whether lower courts can apply statistical methods.
Early in the oral argument, Justice Stephen Breyer briefly sketched the core of a promising approach -- and it's not all that complicated.
In a nutshell: If one party controls the redistricting, if the resulting map treats one party much better than another, if it would do so over a wide range of potential votes (and thus entrench one party), and if it is an extreme outlier compared with what is done in the rest of the country, then it would be struck down -- unless it could be defended by reference to some legitimate and neutral justification.
That's not perfect. It needs work. But it's a good start – and it's a lot better than giving a free pass to the most extreme forms of partisan gerrymandering, which threaten to do catastrophic damage to the very idea of self-government.