In a landmark 5-4 decision issued by Chief Justice John Roberts and the conservative majority, the Supreme Court has rejected challenges to a GOP-drawn map in North Carolina and a Democratic-drawn map in Maryland. In doing so, the Court has ruled that partisan gerrymandering is non-justiciable: in other words, maps can't be challenged in federal courts for bestowing advantage to one party.

In the past few decades, the Supreme Court had wrestled with the issue, with Justice Anthony Kennedy leaving open the possibility that the Court could identify a workable legal standard for how far is "too far" to rein in gerrymandering. But new Justice Brett Kavanaugh sided with other conservatives in declaring federal courts shouldn't wade into this political thicket altogether.

In delivering the opinion, Roberts made clear the Court was not endorsing the practice, writing that "the conclusion that partisan gerrymandering claims are not justiciable neither condones excessive partisan gerrymandering nor condemns complaints about districting to echo into a void. Numerous states are actively addressing the issue through state constitutional amendments and legislation placing power to draw electoral districts into the hands of independent commissions, mandating particular redistricting criteria for their mapmakers, or prohibiting drawing district lines for partisan advantage. The framers also gave Congress the power to do something about partisan gerrymandering in the Elections Clause. That avenue for reform...remains open.

Although the decision might strike reform advocates as a monumental setback, in practice, it remains likely there will be a modest decline in so-called "extreme" partisan gerrymandering in 2021 compared to 2011, owing to several factors that have nothing to do with Supreme Court intervention.

First, new commission regimes installed by legislation or ballot initiative in states including Colorado, Michigan, Ohio, Utah and possibly Virginia promise to temper or remove the most partisan instincts of state legislators from the process. Second, Democrats' success in 2018 governor races in states such as Pennsylvania and Wisconsin means there will be several checks on Republican legislatures that didn't exist in 2011, potentially resulting in stalemates that push more map-making responsibility to state courts.

Additionally, demographic changes and Democrats' success in 2018 House races—including in many districts drawn by Republicans in 2011—means GOP legislators might rethink their approach in places where they retain control. For example, they may have little choice but to draw new Democratic-leaning districts in places like Austin, Texas, and the northern Atlanta suburbs to solidify their grip on neighboring seats.

It's also likely that Democrats will continue to pursue an end-around to courts' unwillingness to take up partisan gerrymandering: suing to overturn GOP-drawn maps on racial gerrymandering grounds. In the last four years, Democratic-aligned attorneys have successfully sued to overturn maps in North Carolina and Virginia this way, resulting in "unpacking" several African-American majority seats.

In removing a cloud of uncertainty over the 2021 redistricting cycle, the Supreme Court dashed many reformers' hopes. But Democrats got better news on the Census citizenship question, as Roberts sided with the Court's liberals in expressing skepticism towards the Trump Administration's legal rationale for adding the question to the form and remanding the case to lower courts for further action.

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