The cases, out of Wisconsin and Maryland, had the potential to reshape political maps across the country by sanctioning or restricting states' ability to draw districts for one party's political advantage.
Republicans created the Wisconsin map after winning full control of the state government in 2011, the first time either party had done that in more than 40 years. Republicans said that type of self-sorting made it virtually impossible to draw a map without creating some heavily Democratic urban districts. In closely divided states like New Hampshire and North Dakota - where U.S. Senate races can be decided by only a few hundred votes - Republican lawmakers have passed voter restrictions that make it harder for Democratic populations to cast ballots.
"The court reasonably could have concluded that a preliminary injunction would have been against the public interest, as an injunction might have worked a needlessly 'chaotic and disruptive effect upon the electoral process, '" the court wrote. The voters contend that Democrats in Annapolis violated their First Amendment rights with the 2011 redistricting by punishing them for their GOP voting history.
Election reformers in both parties had hoped the justices would stop a growing trend in which parties that control state legislatures use the process of redrawing electoral districts after the U.S. census every decade to tighten their grip on power by diluting the clout of voters who tend to support the rival party.
Monday's decision only focused on whether an injunction should have been granted to toss out the boundaries. It now goes back to the lower courts for trial.
The drawing of lines for electoral districts must build community across partisan divides rather than divide people by mutable political identities. Americans remain broadly opposed to gerrymandering; according to a September study from the Campaign Legal Center, 73% of respondents did not want any partisan bias in how districts are drawn, even when it's in favor of their own party.
During oral argument in March, the court's liberal justices said Democrats clearly went too far when they redrew a congressional district won for two decades by a conservative Republican so he would lose in a landslide in 2012.More news: Colombia's James Rodriguez will not start vs. Japan after calf injury
Instead of deciding the constitutional question, however, the court unanimously said that the plaintiffs in the lead case from Wisconsin had not shown that they had suffered the kind of injury that would allow them standing to seek intervention from the courts. Those new standards convinced the Pennsylvania state supreme court to overturn its congressional map as a partisan gerrymander, as well as a federal three-judge panel in North Carolina, which will likely head to the Supreme Court this fall.
Gaddie was hired by Wisconsin Republicans in the course of drawing the state's legislative maps, but, in 2017, he filed a friend of the court brief against the Republicans in the Supreme Court case.
The cases were closely watched around the country, including in OH, where the state's Republican-controlled state government implemented a similarly partisan remap when it redrew congressional district lines in 2011. "This Court is not responsible for vindicating generalized partisan preferences", Chief Justice John Roberts wrote in an opinion all his colleagues joined, which returned the case to a lower court to consider whether the Wisconsin plaintiffs could show their individual votes had been burdened.
Second, the decisions do nothing to the power of state courts to stop partisan gerrymandering under state constitutions. Many believed the justices might use "standing" - or the legal right to bring a case - as an off ramp to avoid the merits in the case.
The plaintiffs alleged that they had a personal stake in the case, "but never followed up with the requisite proof", Roberts wrote.
Critics say Ohio's practice will disproportionately affect minorities, the elderly, and poor voters who move from place to place.
"This is definitely not the end of the road", said Sachin Chheda, director of the Fair Elections Project which organized and brought the lawsuit.
"We just know it is not democratic", Gaddie said, "and therefore despicable, but we don't know if it's illegal".