Gov. Larry Hogan on Thursday vetoed the proposed congressional map that the Maryland General Assembly sent to his desk less than 24 hours earlier, lambasting it as an unfair and partisan and calling on the Justice Department to add Maryland to a redistricting lawsuit filed this week over gerrymandered maps passed in Texas.

But within hours, Democrats, who hold supermajorities in both chambers, convened to override Hogan’s veto.

Hogan (R) and anti-gerrymandering critics vowed to continue fighting the maps in court.

“These maps disenfranchise voters, they violate the Voting Rights Act, and they are in violation of numerous state and federal laws,” Hogan said before signing a veto letter.

He described the map as “more egregious” than the map passed by Republican legislators in Texas, who have been accused of discriminating against Latinos and other minorities with their redrawn congressional and state legislative districts.

“The congressional map drawn in backrooms by party bosses in Annapolis makes a mockery of our democracy, and it is an embarrassment to all that our state stands for,” he said.

The General Assembly had passed the proposed congressional map in both chambers over Republican objections and criticism from anti-gerrymandering organizations — one of which has already threatened “aggressive legal action” against the map. Del. Gabriel Acevero (D-Montgomery) was the only Democrat to vote against the map.

The map, redrawn every 10 years after the census, would solidify Democrats’ advantage in the congressional delegation, retaining seven safe Democratic seats while putting the state’s only Republican congressional district, held by Rep. Andy Harris, in play for Democrats.

Republicans had charged that Democrats redrew Harris’s Eastern Shore-anchored 1st District with the intent of picking up a possible eighth congressional seat under the right conditions in next year’s midterm elections. Democrats argued they drew the district to hop over the Chesapeake Bay into Anne Arundel County because the Bay Bridge connects the county as a community of interest with the Eastern Shore.

The outcome, in any case, is that the 1st District is far more competitive for Democrats, swinging from a district President Donald Trump won by more than 19 points in 2020 to a district Joe Biden would have won by 0.3 points.

In both chambers Wednesday, Republicans urged colleagues to sustain Hogan’s veto, to no avail.

“Just because you have the power to do something doesn’t make it right,” said Del. Susan K. McComas (R-Harford).

Del. Brian A. Chisholm (R-Anne Arundel) called the map a “power grab.”

“It’s about shutting down the voice of anybody that’s in opposition of the majority party,” he said.

Other districts were criticized for their unusual shapes and tentacles, which Republicans argued were probably for the sole purpose of capturing more Democratic voters.

The 3rd Congressional District — which state Sen. J.B. Jennings (R-Harford) compared to a Tyrannosaurus rex — spans from Montgomery County to the Susquehanna River and the Pennsylvania border while dipping into Baltimore City, too, with what Jennings called the dinosaur’s arm. The 8th Congressional District takes in much of Carroll County but then has a long tentacle reaching into Montgomery County at the D.C. border.

Democrats argued that, while maybe not pretty, the shapes of the districts represented traffic patterns and social patterns of Marylanders, representing modern life rather than hewing to county boundaries drawn centuries ago. Republicans mocked those justifications, noting that D.C. suburban areas could not be considered communities of interest with the northern rural parts of the state no matter how Democrats sliced it.

Democrats also argued throughout the debates that they believed the map followed the Voting Rights Act, protecting minority populations and reflecting the state’s growing diversity.

In his veto letter, Hogan offered comparisons of the racial makeup of the districts drawn by his citizens commission versus those drawn by legislators. He said that the citizen plan has four districts in which minorities constitute more than 50 percent of the voting-age population but that the map approved by the legislature has three districts that have the same racial makeup. He said “true representation of Maryland” would allow minority voters to elect a candidate of their choice in at least 50 percent of the districts.

On Wednesday, Fair Maps Maryland said it was exploring legal action against the map. Hogan said the map will be the subject of state and federal litigation.

“The legislature may have temporarily achieved their partisan goal today, but we can assure them that the courts will have the final say on this matter,” Fair Maps Maryland spokesman Doug Mayer said in a statement. “We’ve not yet begun to fight.”