MIAMI — A state judge in Florida said on Wednesday that an aggressively drawn congressional map adopted by Republicans was unconstitutional because it diminished Black voters’ electoral power.
After a hearing, Judge J. Layne Smith of the Leon County Circuit Court said from the bench that he would issue a formal order on Thursday or Friday blocking the map, which has been challenged by several voting rights groups.
The administration of Gov. Ron DeSantis, a Republican, will appeal.
“As Judge Smith implied, these complex constitutional matters of law were always going to be decided at the appellate level,” Taryn Fenske, the governor’s spokeswoman, said in a statement, adding that the administration was confident the map passed legal muster.
The judge’s office would not immediately confirm the ruling, which The Associated Press reported and the office of Marc E. Elias, a Democratic lawyer whose voting rights group has been involved in litigating the case, described in a post on the organization’s website.
The map would add four congressional districts that lean toward the G.O.P. and eliminate three that tilt toward Democrats. That would most likely give Republicans control over 71 percent of Florida’s 28 seats — even though recent election results show the state, a perennial presidential battleground, to be much more evenly divided politically. Former President Donald J. Trump won the state in 2020 with 51.2 percent of the vote.
Republicans in the State House and Senate passed the map after Mr. DeSantis vetoed an earlier version and demanded the redrawing of two districts held by Black Democrats. Lawmakers eliminated the district held by Representative Al Lawson of Jacksonville and diluted the Orlando district held by Representative Val Demings of Orlando. Ms. Demings is leaving her seat to challenge Senator Marco Rubio, a Republican.
“We know the new congressional map proposed by the governor diminishes the voting rights of Black voters, yet the governor chose to waste taxpayer dollars convening a special session to double down on diminishing minority voting rights,” State Representative Joseph Geller of Aventura, the ranking Democrat on the House Redistricting Committee, said in a statement.
The final decision on the map could ultimately lie with the Florida Supreme Court, which has turned more conservative in recent years after the retirement of several justices who have been replaced by Mr. DeSantis’s appointees. The court’s decision could uphold or strike down an anti-gerrymandering amendment to the State Constitution enacted by Florida voters in 2010, which required compact districts that do not favor one political party.
It is unclear whether a ruling on an appeal would arrive in time for the November elections.
Judge Smith was first appointed to the bench by former Gov. Rick Scott, a Republican, and then elevated to the circuit court in 2020 by Mr. DeSantis.