The practice of “gerrymandering” – drawing congressional districts lines in ways that favor one group of voters by diluting the votes of others – is as old as Congress itself. The term was coined in 1812 to describe a district drawn by Massachusetts Governor Elbridge Gerry that looked like a salamander.

Federal courts have prohibited gerrymandering in cases where legislators drew maps designed to discriminate against African-American and Hispanic citizens. But courts have not applied the same rules to cases of partisan gerrymandering, in which one party draws lines to dilute the impact of another party’s voters.

That trend is changing. In a series of cases, federal courts have struck down electoral maps in North Carolina, Maryland, Wisconsin, Michigan, and Ohio. Soon the Supreme Court will weigh in with a ruling that may determine how voting districts are drawn after the 2020 Census.

Before the end of June, the Supreme Court is expected to make a decision in cases challenging redistricting plans by both political parties – Republicans in North Carolina, and Democrats in Maryland. Both cases involve extreme instances of gerrymandering, where lawmakers were explicit about their motives to draw congressional districts in ways that created a political majority. The Maryland case is before the Supreme Court for a second time. Last year, the court declined to make a decision and sent the case into another round of appeals.

In the past, the Supreme Court has struggled to decide when partisan gerrymandering crossed a constitutional line. Some experts believe this time is different. “We’ve clearly hit a tipping point in partisan gerrymandering litigation around the country,” Thomas Wolf, a lawyer at the Brennan Center, told the Washington Post. “The lower courts are showing the way – that courts can make sense of these problems and solve them in clear ways.”

Voting rights advocates hope that the Supreme Court will back up the lower court rulings that struck down the redistricting plans and create a new legal standard to judge when partisan gerrymandering has gone too far. Allison Riggs, an attorney for the League of Women Voters in the North Carolina case, argued that the case offers such an extreme example of partisan gerrymandering that the courts would “implicitly endorse unfettered partisan manipulation in redistricting by declining to rein [it] in.”

Defenders of the redistricting plans argue that the Constitution doesn’t provide any legal standards to evaluate gerrymandering claims. They believe that if the Supreme Court does get involved, it could open the floodgates to hundreds of cases and leave courts mired in political disputes for years to come. In place of court challenges, they point to ballot initiatives as an effective way to address gerrymandering.

Ballot initiatives have been used in several states to take control of redistricting away from state legislatures and place it in the hands of independent or bipartisan redistricting commissions. Independent redistricting commissions are operating in a growing number of states, and already have withstood a Supreme Court challenge in 2015.

Whether or not the Supreme Court sets limits on gerrymandering before the 2020 election, voters in each state can hold their lawmakers accountable. Citizen-led campaigns to change redistricting laws and create independent commissions are on the rise, and the Brennan Center is tracking several reform bills in state legislatures and Congress.

For a deeper dive into how redistricting works, how your state draws district lines, and what you can do about it, check out A Citizen’s Guide to Redistricting from the Brennan Center, the Activist Guide to Redistricting Reform from Common Cause, and Designing Independent Redistricting Commissions by the Campaign Legal Center.