Maryland Attorney General Brian Frosh (D) says he will appeal to the Supreme Court after a ruling last week that threw out the state’s congressional voting map. (Doug Kapustin/For The Washington Post)

Maryland’s attorney general on Thursday appealed to the Supreme Court a ruling that threw out the state’s congressional voting map and ordered officials to redraw lines before the 2020 election.

Brian E. Frosh (D) is asking the high court to quickly review the three-judge panel’s unanimous decision last week that found Democratic mapmakers violated the First Amendment rights of Republican voters.

The long-running lawsuit has been before the Supreme Court twice, most recently in June when the justices avoided answering when extreme partisan gerrymandering is unconstitutional in cases from Maryland and Wisconsin.

Frosh’s decision to appeal, rather than abide by the call to create a new map, puts him at odds with Republican Gov. Larry Hogan. Hogan won reelection last week and has pushed three times for a constitutional amendment that would have an independent commission redraw boundaries.

Under state law, the attorney general can proceed in court independent of the governor and as part of the office’s role to defend measures passed by the General Assembly.

“It’s outrageous that the Attorney General and legislative leaders are continuing to fight against free and fair elections, even in the wake of a unanimous federal court ruling. The governor will continue to push for nonpartisan redistricting reform, and will once again introduce legislation in the next session,” Hogan spokeswoman Amelia Chasse said.

Redistricting decisions can be appealed directly to the Supreme Court, which must uphold or reverse the rulings. Maryland announced its appeal to the high court in a new filing Thursday. The state also asked the panel to put its order for a new map on hold until the Supreme Court acts.

Frosh’s office and the Republican challengers reached an agreement to move quickly to give the high court time to consider the case this term — and allow time for the adoption of a new map, if necessary.

“Time is of the essence in this case,” Michael B. Kimberly, the attorney for the GOP voters, said in a court filing.

Nationally, voters are embracing efforts to take redistricting out of politicians’ hands. Last week, ballot measures passed overwhelmingly in three states to make the drawing of electoral districts less partisan.

Advocates for redistricting reform in Maryland see Frosh’s appeal as a chance for the Supreme Court to spell out clear rules that would apply to every state in the country. A national standard would undercut the argument from Maryland Democrats that choosing nonpartisan redistricting here is tantamount to unilateral political disarmament, since Republican-dominated states could still send lopsided delegations to Congress.

“To not hear this case would be a bad outcome because we would end up with a ruling that only applies to Maryland,” said Damon Effingham, executive director of Common Cause Maryland. “It would still be incredibly difficult to get the reforms that we’re hoping for.”

Maryland’s Democratic leaders are publicly silent about the court ruling, but behind the scenes, they criticized it as contradictory and difficult to implement. They rooted for Frosh to appeal.

The lawsuit centers on the 6th Congressional District in Western Maryland, which was redrawn in 2011 to include parts of heavily Democratic Montgomery County. Republican Roscoe G. Bartlett had represented the district since 1993. But after the map was redrawn in 2012, he lost to Democrat John Delaney. Last week, Democrat David Trone won there, succeeding Delaney.

The day after the election, a special three-judge panel declared the congressional map unconstitutional and gave elected officials until March 7 to send the court a new design. The judges — Paul V. Niemeyer of the 4th Circuit, Chief District Judge James K. Bredar and U.S. District Judge George L. Russell III — advised the state to “establish a neutral commission” to develop its plan. If state officials cannot agree, the court set up a commission to redraw the boundaries.

“It is impossible to flip a seat to the Democrats without flipping it away from the Republicans,” Niemeyer wrote. “There can be no doubt that at every stage of the process, the State’s Democratic officials who put the 2011 redistricting plan in place specifically intended to flip control of the Sixth District from Republicans to Democrats and then acted on that intent.”

Frosh’s office argued that the party shift could be attributed to other factors in the 6th District and that individual voters did not show that they had been singled out or harmed by the new configuration.

The judges, however, were unanimous that Democratic mapmakers violated the GOP voters’ First Amendment rights of political association by making it harder for the party to organize and to raise money.

The Supreme Court could resolve the case without holding oral arguments, or the justices could consider combining it with another gerrymandering case from North Carolina, where Republican legislative leaders have appealed an August ruling that found “invidious partisan discrimination” to favor Republicans over Democrats in 2016 congressional races. The court could also put one of the cases on hold until the other is resolved.

In Annapolis, Democratic lawmakers and aides have struggled to figure out how to implement the panel’s ruling and follow the directive to protect Republicans’ political association rights but also remap without considering party affiliation or past voting data.

They have also raised concerns about redrawing maps for the 2020 election based on population data that is eight years old when the lines will need to be drawn again after the 2020 Census. Multiple do-overs could mean that voters in Western Maryland would vote in different districts in 2018, 2020 and 2022.

Hogan aides anticipate fewer problems in fixing the map, yet acknowledge the logistical hurdles to finishing by March.

Under Maryland state law, the governor or the General Assembly can recommend a new map, with the governor traditionally taking the lead. The legislature, which has a Democratic supermajority, must approve it, and then the governor can sign it into law or veto it.

Maryland residents widely favor having an independent commission draw political boundaries, according to a 2017 Goucher Poll that showed 73 percent favor the approach, with only 20 percent saying politicians should do the design.

Mileah Kromer, a political scientist who has surveyed voters on redistricting, said she expects the court’s ruling will further increase public support for an independent commission and add urgency to Hogan’s efforts.

“People like the sound of the independent commission,” said Kromer, who directs the Goucher Poll. “But this will make it real to them.”