Then in December, the court said it would hear the case about Maryland’s 6th congressional district, but provided no further explanation about why it was adding a second redistricting case.

Democrats who controlled redistricting in Maryland in 2011 made a conscious decision to try to increase the party’s control of congressional districts from 6-2 to 7-1, said Michael Kimberly, the lawyer representing the Republican challengers.

They took a district that had been centered in rural, Republican-leaning northwestern Maryland, where a longtime Republican incumbent won by 28 percentage points in 2010 and turned it into a district that took in some Democratic Washington, D.C., suburbs and elected a Democrat who won by 21 percentage points in 2012.

The change violated the First Amendment rights of the Republican voters, Kimberly said.

Maryland Attorney General Brian Frosh, a Democrat, said in defending the district that it is competitive for both parties and has elected a moderate Democrat. In 2014, a friendlier year for Republican candidates, Democratic Rep. John Delaney’s victory margin dropped to less than 2 points, though it rose again in 2016.

In some ways, the Wisconsin and Maryland cases complement each other. In Wisconsin, the justices have a broad theory about partisan line-drawing. The lower court that ruled for the Democratic challengers concluded that the districting plans were drawn to discriminate against Democrats, the Republicans’ advantage would endure even in the face of a strong Democratic showing at the polls and the plans could not be explained by other, non-partisan reasons.

In Maryland, the single-district approach looks a lot like the way civil rights groups try to prove that race played too large a role in the drawing of districts. It would be both a more limited approach than the Wisconsin case, but also feel more familiar to justices who have decided many claims of racial bias in redistricting.

With two cases before them, the justices now have one in which each party is complaining about the other.

That could be significant based on Chief Justice John Roberts’ stated distaste for putting the court’s credibility at stake in politically charged cases.

“We’ll have to decide in every case whether the Democrats win or the Republicans win,” Roberts said in the Wisconsin arguments.

Another possibility is that the justices could already have decided that there’s a procedural problem in the Wisconsin case, limiting their ability to address the merits of the Democratic voters’ claim.

However the court views the two cases, it seems increasingly likely that a decision striking down districts won’t result in any changes this year. The court frowns on making these sorts of changes so close to an election. The deadline to get on the primary ballot in Wisconsin is June 1. Maryland’s deadline was last month.

The court also has blocked new congressional districts in North Carolina.

Only in Pennsylvania, where the state Supreme Court invoked the state constitution to strike down the congressional map, has a new map been put in place. The Supreme Court refused an emergency request from Pennsylvania Republicans to block it.