“Partisan gerrymandering is nothing new,” writes Chief Justice John Roberts near the beginning of his opinion in Rucho v. Common Cause. “Nor is frustration with it.” The question is what, if anything, federal courts ought to do about it. The answer the chief justice and the four other Republican-appointed justices have endorsed, journalists have been reporting, is nothing.

Actually, judges have a very effective weapon to limit, though not prohibit, partisan districting, which we’ll get to later. But first, let’s be clear that the chief justice is right about the history of the issue. He is correct, first of all, in disagreeing with Justice Elena Kagan’s suggestion in her dissent that partisan districting has gotten much more common and effective in recent years.

The word “gerrymander” is a clue. It’s named after Elbridge Gerry, delegate to the Constitutional Convention and fifth vice president of the United States. As a Jeffersonian in Massachusetts, he packed heavily Federalist towns into a single salamander-shaped congressional district in 1812. That was 207 years ago.

The fact is that once you are committed to having legislators elected by districts, and once you have competitive political parties, it is going to matter how you draw district lines. In fact, any competent partisan will struggle to draw them to its maximum advantage.

The founders, following the example of the British Parliament, quickly opted against at-large elections and proportional representation in states, something perfectly permissible under the Constitution, and in favor of election by geographically defined districts. And in 1842, Congress required states to draw compact and contiguous districts of equal population, influenced perhaps by Britain’s 1832 Reform Act, which eliminated representation for towns with no population and provided representation for growing industrial cities.

In 1929, Congress repealed its requirements for contiguity and equal population, and legislatures’ subsequent refusal to update districting plans in line with population changes inspired lawsuits. The Supreme Court dismissed them in the 1940s, but in 1963 and 1964 it ruled that congressional and legislative districts within each state had to be of equal population. That requirement, scarcely mentioned in Rucho, has operated quietly as a severe limit on politicians’ ability to gain partisan advantage from districting. And its arithmetic standard is easily policed by courts.

As co-author of The Almanac of American Politics for more than 40 years, I have closely followed redistricting plans in every state and in every cycle after the censuses of 1960, 1970, 1980, 1990, 2000, and 2010. Democrats dominated the redistricting processes in the 1970s and 1980s, with little adverse comment; conservatives still yearned for the preequal population plans that favored agrarian districts, and liberals were delighted by plans concocted by the likes of California’s Rep. Phil Burton.

But liberals were suddenly shocked and appalled when Republicans came to dominate the redistricting process in big states such as Texas, Florida, Pennsylvania, Ohio, and Michigan in the cycles following the 2000 and 2010 censuses.

Changes in political demographics helped Republicans there and elsewhere. Democratic voters have increasingly been concentrated in central cities, a few sympathetic suburbs and university towns; Republican voters are spread more evenly around the rest of the country. Any equal-population plan tends to work against a party which wins by margins such as 80-20 in a few districts and that loses by margins closer to 55-45 in many more.

Justice Kagan expressed liberals’ frustration and rage (not too strong a word) and portrayed partisan districting as fatally undermining electoral democracy. To one who has followed the fate of redistricting plans in detail over the last half-century — and who has seen how the intentions of redistricters have been frustrated by changes in public opinion and political alignments — these complaints seem overwrought.

Time and again, aggressive partisan redistricting plans, from those of California Democrats in the 1960s to those of Pennsylvania Republicans in the 2000s and 2010s, have backfired on their makers. Despite Republicans’ redistricting advantages in the last two decades, Democrats won big House majorities in 2006, 2008, and 2018.

In any case, partisan redistricting will be on the wane in the 2020 census cycle. Michigan, Ohio, and Colorado have joined California, Washington, and Iowa in creating redistricting commissions which are supposedly nonpartisan (but which, as Capital Research Center scholars have shown, effectively lean Democratic). A Florida referendum limits Republican redistricters there, and the 2018 governor elections left fewer states with total partisan control. In partisan terms, redistricting in the 2020 cycle looks like it will be a wash.

So it’s wise to shut the courtroom door to lawsuits which risk politicizing the federal courts by requiring judges to decide cases with “no judicially discoverable and manageable standards.”