It’s become an accepted truth of modern politics that Republican electoral prospects go up as the number of voters goes down. Conservatives have known this for a long time, which helps explain their intensifying efforts to make it harder to vote, or to eliminate large numbers of people from political representation entirely.

On Monday, the Supreme Court unanimously rejected one of the more extreme attempts — a lawsuit from Texas that aimed to reverse longstanding practice and require that only eligible voters be counted in the drawing of state legislative districts.

Texas, like virtually everywhere else in the country, applies the court’s “one person, one vote” rule by counting all people living in a district, regardless of whether they can vote. The legal challenge to that practical approach came from white conservatives living in Republican-leaning rural areas. They said this diminished their political power and increased the political power of Texas’ urban areas, where more minorities — particularly Latinos, who are disproportionately not citizens — tend to live.