The Supreme Court announced Friday it will again consider whether lawmakers violate the U.S. Constitution when they draw electoral districts to severely benefit a specific party.

The court said it plans to hear two cases on the matter in March. One, Common Cause v. Rucho, involves North Carolina’s congressional map. The other, Benisek v. Lamone, involves a single Maryland congressional district.

Congressional redistricting is done once every 10 years, and the next round is set to take place in 2021. The March cases are widely seen as among the last opportunities for the Supreme Court to place limits on partisan gerrymandering before then. In 2011, Republicans, facing no constitutional limits, used technology to draw remarkably precise districts that gave them entrenched electoral power for the next decade.

In its last term, the Supreme Court heard a pair of closely watched cases involving excessive gerrymandering, including the Maryland suit. The justices punted on the issue and sent the cases back down to lower courts for further consideration.

Advocates had hoped they could sway then-Justice Anthony Kennedy to their side in last year’s cases, but many are less optimistic that Justice Brett Kavanaugh, Kennedy’s replacement, would vote to strike down a congressional plan because of partisan gerrymandering.

In both of last year’s cases, lower courts struck down gerrymandered districts, saying they were so excessively drawn to benefit one political party that they violated the U.S. Constitution.

“Whether it is Democrats or Republicans manipulating the election maps, gerrymanders cheat voters out of true representation,” Karen Hobert Flynn, president of the government watchdog group Common Cause, said in a statement. “The Supreme Court has the opportunity to set a clear standard that will restore a meaningful vote to millions of Americans disenfranchised by gerrymanders in Maryland, North Carolina and across the country.”

A panel of three federal judges struck down North Carolina’s entire congressional map in August, saying it was so severely drawn to benefit Republicans that it violated the First and 14th Amendments, as well as Article I of the U.S. Constitution. Republicans controlled the redistricting process in 2011 and drew congressional districts to give their party a 10-3 advantage. The GOP has reaped the benefits of that advantage in each election since, even after a 2016 revamp of the map to address racial gerrymandering. (The results of one 2018 congressional race are not yet finalized.)

The Maryland case involves a challenge to a single congressional district, which challengers accused Democrats of drawing to intentionally weaken GOP votes and swing the district from Republican to Democratic. Michael Kimberly, a lawyer representing the plaintiffs in the suit, argued before the Supreme Court last year that Democrats had intentionally targeted Republicans because of their political views. The justices seemed a bit skeptical of that argument, and pressed Kimberly to explain to what extent lawmakers could take political views into consideration when drawing electoral districts.

The Supreme Court has long struggled with where to place a constitutional boundary when it comes to partisan gerrymandering, or if one even exists at all. In the 2004 case Vieth v. Jubelirer, four justices wrote that partisan gerrymandering was not an issue where there were any manageable standards for courts to decide. Kennedy, writing separately, said that a standard might exist, extending an invitation for advocates to come back to the court with one.

Advocates did just that in the court’s last term, offering an array of standards in a case called Gill v. Whitford involving gerrymandered state legislative districts in Wisconsin. But the court punted on the case, sending it back to a lower court to determine whether the plaintiffs in the case had standing to bring a suit. The Supreme Court said that voters have to show they have suffered a specific injury in their specific districts to bring a partisan gerrymandering suit.

The North Carolina case is being closely watched because the three-judge panel pointed to the conditions the Supreme Court laid out in Gill and said the North Carolina plaintiffs met them.