Demonstrators rally with cutouts of congressional districts in front of the Supreme Court before oral arguments on Benisek v. Lamone in Washington on March 28. (Joshua Robert/Reuters)

As the Supreme Court increasingly confronts cases challenging partisan gerrymandering, one underlying question appears to be: Is this getting worse? The answer is yes. There are some structural reasons for that.

For years, party control of the House was stable. Now it’s regularly up for grabs. 

For at least 50 years, from 1950 to 2000, partisan control of the House was never perceived to be at stake during any redistricting cycle. The Democratic Party dominated the House; the Republican Party consigned itself to being the permanent minority; and no one in either party thought partisan control of the House could switch hands in any upcoming election.

From 1958 to 1994, the average number of seats the Republicans held was 170 — far from the 218 needed for a majority. In fact, going all the way back to the New Deal, Republicans controlled the House for, remarkably, only four years out of the 60 leading up to 1994.

All that changed in the stunning 1994 Newt Gingrich-led revolution, when the Republicans seized control of the House for the first time since the early 1950s. Since then, as Frances E. Lee documents in her superb new book, “Insecure Majorities,” we have been living through a dramatically transformed world of competitive party politics. We have experienced a more sustained era of political parity in the House — and in our politics, more generally — than at any time since the Civil War. Partisan control of the House has flipped back and forth between the parties, as it may again in 2018.

Just as important, the margin of control for either party in power has been consistently narrow. Partisan control of the House appears to be up for grabs in nearly every election now. And both parties have seen it that way since 1994.

We’ve only had two redistricting cycles in this new era

We have had only two redistricting cycles (2000 and 2010) in this transformed political terrain. When the stakes are so high that partisan control of the House might hang in the balance, more aggressive partisan efforts to gerrymander will, not surprisingly, flourish.

A dramatic shot in this battle was sounded during the 2000s, which involved the high-profile mid-decade “re-redistricting” of Texas. Rep. Tom DeLay (R-Tex.), the then-House majority leader, pressed the Republican-controlled Texas legislature to throw out the existing congressional districts and draw a new map to create more Republican seats — even though a valid post-census map was already in place. Usually, state legislatures redraw their districts once a decade, when the new census results come out. For a state to redistrict its congressional seats again in the middle of the decade was almost unheard of. DeLay was excoriated in much of the national media for this tactic. One could argue that the action was justified, because the existing plan was a Democratic gerrymander that suppressed Texans’ large swing toward Republicans since the 1990s. But the tactic was still shocking and a harbinger of what was soon to come.

Even so, the opportunity to gerrymander was less widespread in the 2000 round of redistricting than after the 2010 Census — because fewer state governments were under one party’s control. In 2000, 21 state governments had governorships and state legislatures controlled by one party; 15 of those were Republican. But by 2010, 33 state governments were under one-party control, 22 of them Republican.

In other words, in the round of redistricting being litigated before the Supreme Court and other courts, far more state governments had both the motivation and the power to aggressively gerrymander their districts to give one party an edge.

The current Supreme Court case concerning Maryland provides a good example. There, Democrats controlled the redistricting process and candidly admitted they were trying to flip one district from Republican to Democratic. Why care so much about changing the partisan makeup of a single district? It wasn’t because Maryland’s representation in Congress would be significantly enhanced by a 7-to-1 rather than a 6-to-2 Democratic delegation. It was because, with partisan control of the House potentially at stake, each party with unified control of state government will face strong incentives to squeeze out every single additional district win possible for their party. And because the Democrats need to flip only 24 or so seats to gain control, every district matters.

More and more, people see the stakes in politics as existential

In other words, this decade of redistricting combined a toxic mix of exceptionally powerful incentives to gerrymander — and many more one-party states able to do it.

The modern era of regular decennial redistricting began in the 1970s, when every state began to have to redraw districts every decade, after the new census, to meet the equal-population requirements of the Supreme Court’s one-vote, one-person doctrine. Since then, we have not had a redistricting cycle with as virulent a combination of incentive and capacity to gerrymander.

What’s more, our politics are so polarized that partisan political conflicts have come to seem existential. Each party believes that, if the other gains control, the very identity of the United States will be compromised. The perceived stakes could not be much higher.

On top of these structural changes in politics, other more widely recognized factors contribute to making gerrymandering worse today. Technological changes make precision gerrymandering easier. Voters are far more polarized, which makes gerrymanders more reliable and enduring because voting patterns are more stable and easier to predict.

But while the ability to gerrymander successfully has improved, the transformation in the structure of our politics has changed even more dramatically. Control of our political institutions has been evenly divided over an exceptionally sustained period. And the nature of our hyperpolarized, existential politics has raised the stakes even more.  It’s no wonder that we are seeing such aggressive partisan gerrymandering in so many places.

Gerrymandering has existed since our first elections.  But partisan gerrymandering today is far more extreme and pervasive than in the past. And unless something changes — such as meaningful constitutional constraints or measures that give the power to draw districts to independent institutions rather than to partisan state legislatures — every reason exists to expect it will get worse still.

Richard H. Pildes is the Sudler Family Professor of Constitutional Law at New York University School of Law.