The Supreme Court once again passed up a historic opportunity to finally put some limits on partisan gerrymandering. In a pair of cases from Wisconsin and Maryland, the court declined to take on the big question: When does gerrymandering, the drawing of districts to benefit the political party in control, go so far as to be illegal?

The result is disappointing but not devastating: The cases will continue, and the court has left open several paths to rein in gerrymandering. For the sake of our democracy, the court needs to act soon.

There are good reasons to be optimistic. The justices did not throw the cases out of court, or say partisan gerrymandering is legal. Either or both would have been easy options if the court didn’t ultimately want to tackle the big issue.

Instead, the cases were sent back to the lower courts to iron out technical legal issues or to go to trial.

In these cases, that means requiring the Wisconsin plaintiffs to meet the requirement for “standing,” proving that they are the right people to bring their claims, and requiring the Maryland plaintiffs to prove their case in court before requesting a change in the map.

The court told us years ago in Vieth vs. Jubelirer that extreme partisan gerrymandering is unconstitutional. What has repeatedly vexed the justices is how to identify when, exactly, partisanship in map-making crosses into extreme territory. Maps like those in Wisconsin and Maryland offer an easy-to-understand answer: Legislators cross the line when they use redistricting to entrench artificial majorities in power and shield their party from accountability to voters.

This kind of gerrymandering is deeply, fundamentally wrong. Extreme gerrymanders wreak havoc on voters’ ability to elect the kind of representative and accountable legislatures that the Constitution guarantees them.

Wisconsin Republicans won just 48.6 percent of the statewide vote for the state’s general assembly in 2012, but scored 60 out of the assembly’s 99 seats. The GOP in Wisconsin has maintained its majority ever since.

Meanwhile, Maryland Democrats have had a decade-long grip on seven of their state’s eight congressional seats, courtesy of a gerrymander that moved around hundreds of thousands of voters to maximize Democrats’ advantage.

Add North Carolina’s 2016 congressional gerrymander to that list. By any measure, North Carolina Republicans crossed the line when they flat out proposed — in the words of Rep. David Lewis — “to draw the maps to give a partisan advantage to 10 Republicans and 3 Democrats” and then proceeded to do just that, brazenly declaring the end result a “political gerrymander.” This purple state, which voted in 2016 for a Republican president and a Democratic governor, is now stuck with a hard-right legislature that is trying to undermine any checks on its power.

The court is well aware of the seriousness of the issue, and that it is uniquely situated to solve the problem of partisan gerrymandering. Time is short. A “merits” decision in this term would already have been too late to fix maps for the 2018 elections. But there is still a chance for change before 2020 if the court queues up more cases for its coming term. Action is especially needed before 2021, when every congressional and state legislative map in the country will be redrawn following the 2020 census.

The next best opportunity to limit partisan gerrymandering is in the case challenging North Carolina’s 2016 congressional gerrymander, which is sitting on the court’s doorstep. Drawing on the writings of Justice Anthony M. Kennedy (the swing justice on this issue), Justice Elena Kagan suggested that the court could focus on how partisan gerrymandering burdens voters’ 1st Amendment freedom of association, weakening their right to band together in a party to elect the candidates they want.

This approach would enable either voters or their parties to challenge a state’s whole redistricting plan. All that is left is for the court to follow that map.

The only remaining question, we hope, is when will the court finally declare what every American already knows: It is unconstitutional for politicians to lock their party into power, and we can tolerate it no longer.

Thomas P. Wolf is counsel for the Democracy Program at the Brennan Center for Justice at New York University School of Law. Wendy R. Weiser is director of the Democracy Program.