But now the North Carolina House map could force him and other justices to confront the issue head-on. The redrawing of Maryland’s House map by Democrats was also baldly political, ousting a 20-year Republican incumbent by infusing the rural 6th District with tens of thousands of urban Democrats. But compared with the lawmakers in North Carolina, the Maryland Democrats were restrained, turning down maps that would have wiped out the state’s other Republican-leaning House district as well.

Created three years ago, the North Carolina map was drawn for overtly partisan reasons. Indeed, the Republican chairman of the state House Elections Committee, Representative David R. Lewis, opened the drafting session by saying, “I acknowledge freely that this would be a political gerrymander.” Republicans ordered that the next map create “as many districts as possible in which G.O.P. candidates would be able to successfully compete for office.”

The result, drawn by the master Republican redistricting strategist Thomas B. Hofeller, met that mandate. It anchored three overwhelmingly Democratic districts in liberal cities — Charlotte, Raleigh and Durham. The remaining urban strongholds, in Asheville, Fayetteville and Greensboro-Winston-Salem, were filleted along party lines, with their most Democratic areas absorbed by otherwise rural Republican territories.

Democrats in the state had done their share of gerrymandering in the past, but it was nowhere near what the Republicans were now doing.

The map eliminated any competition for House seats in all but the most exceptional circumstances. In November, amid the strongest national Democratic electoral performance since Watergate, only one of the 10 Republican-held House seats was in serious jeopardy (that race, in the 9th Congressional District, was marred by election fraud complaints and will be rerun this summer). Democrats won the three districts that were gerrymandered in their favor by an average of 45 percentage points.

That highlights collateral damage from gerrymanders that is sometimes overlooked: Not only do they entrench a majority party, but they weaken the opposition as well. Candidates don’t want to run losing races, and donors and parties don’t want to support them.

Pete Glidewell can testify to that. Mr. Glidewell, a real-estate agent and Democratic activist in Elon, about 15 miles from Greensboro, ran in 2016 against the incumbent Republican in the newly drawn Sixth Congressional District, Mark Walker. Mr. Walker had won in 2014 with nearly 59 percent of the vote; Mr. Glidewell was the only Democrat to oppose him. “I thought I was better qualified than him,” he said. “I still do.”