The high court also ruled against a challenge to a map in Wisconsin that had been contested by Democrats.
The court’s rulings on technical grounds did not address the larger question in both cases: Just how far may mapmakers of either party go in pursuit of political advantage?
To government watchdog groups, Maryland’s meandering 6th District is an example of how one state party — in this case, Democrats — used redistricting to its advantage by reconfiguring a district once dominated by Republicans.
The district stretches from the liberal Washington suburbs of Montgomery County to conservative western Maryland. The lines were redrawn after the 2010 census, enabling Democratic newcomer John Delaney to defeat Republican longtime Rep. Roscoe G. Bartlett in 2012.
Jerry DeWolf, one of the seven Republican plaintiffs in the redistricting case, expressed disappointment in the ruling Monday.
“It’s time to get this gerrymandering behind us,” said the Keedysville man, chairman of the Washington County Republican Central Committee. “I think we can do better as a society, and it’s time we get back to citizens electing their representatives instead of the politicians choosing their voters.”
In a state where Democrats outnumber Republicans two to one, Maryland’s mapmakers turned an eight-member House delegation that was split four-four in 2000 into one that now has seven Democrats and one Republican.
The Supreme Court heard oral arguments in the case in March. The voters contended that Democrats in Annapolis violated their First Amendment rights with the 2011 redistricting by punishing them for their GOP voting history.
In a friend-of-the-court brief, the good-government group Common Cause said Democrats decided "to take a meat cleaver and chop the Sixth District almost in half."
The case focused on whether a federal court should have immediately blocked Maryland election officials from holding congressional elections under the new map.
The lower court had declined to take that step, disagreeing with Republicans that using the Democratic-drawn map would result in “a manifest and irreparable injury.”
Monday’s decision focused only on whether an injunction should have been granted to toss out the boundaries. The justices, in their unsigned opinion, did not dismiss the case as a whole. It now goes back to the lower courts for trial.
“The case is far from settled,” DeWolf said.
The lawsuit, filed in 2013, drew renewed interest last year, when lawyers sharply questioned former Gov. Martin O’Malley and General Assembly leaders about the motivations behind the 2011 congressional redistricting.
In a deposition, O’Malley acknowledged what was widely known but rarely said: Maryland Democrats used the redistricting to flip the 6th Congressional District from a reliably Republican seat to one far more competitive for their party.
Gov. Larry Hogan, a Republican, has called for a nonpartisan redistricting commission. Maryland Democrats have rejected that call, saying that surrendering their power to draw the map while Republicans in other states keep theirs would amount to unilateral disarmament.
In the Wisconsin case, a lower court agreed with Democrats that partisan redistricting could go too far and indeed, did. Republicans in Wisconsin hold a huge edge in the legislature even though the state is closely divided between Democrats and Republicans.
But the Supreme Court said the plaintiffs had failed to prove that they have the right to sue on a statewide basis, rather than in individual districts. The Democrats now will have a chance to prove their case district by district.
The high court could decide soon to take up a redistricting case from North Carolina that seemingly addresses some of the high court's concerns. The lawsuit filed by North Carolina Democrats has plaintiffs in each of the state's 13 congressional districts. As in Wisconsin, the North Carolina population is closely divided between the parties, but Republicans hold a 10-3 edge in congressional seats.
Chief Justice John Roberts, writing for the majority in the Wisconsin case, cast doubt on the constitutionality of partisan gerrymandering. He wrote that the Supreme Court's role "is to vindicate the individual rights of the people appearing before it," not generalized partisan preferences.
The usual course when the justices find that parties to a lawsuit lack the right to sue, or standing, is to dismiss the case. But "This is not the usual case," Roberts wrote.
So the voters who sued will be able to try to prove they have standing.
"This is definitely not the end of the road," said Sachin Chheda, director of the Fair Elections Project, which organized and brought the lawsuit.
"There is no vindication for the state's rigging of the maps and disenfranchising of our voters here," Chheda said. "We know as well today as we did when we started that our democracy is threatened and we need to return the power to the people."
Republicans hold a 64-35 majority in the Wisconsin Assembly and an 18-15 majority in the Senate. Republican state Senate Majority Leader Scott Fitzgerald, who defended the maps, had no immediate comment but promised to have reaction after reading the ruling.
The Maryland lawsuit offered the court a more limited approach to dealing with the issue because it involves just one district that flipped from Republican to Democratic control after the 2011 round of redistricting.
Again, though, the justices declined to decide any of the big questions before them: Whether the courts should even be involved in the political task of redistricting, is there a way to measure how much politics is too much and do the particular plans being challenged cross that line.
The Associated Press contributed to this report.