Congressional District 23 cuts across a rural swath of southwestern Texas, from the state’s border with New Mexico, hundreds of miles south along the Rio Grande, stretching east to San Antonio. It’s among the least densely populated terrain in the country—and the most electorally disputed. The district was created in 1967, two years after the passage of the Voting Rights Act. The voters of District 23 sent a Democrat to Congress every term until the 1992 election. At that point, following the 1990 census, which gave Texas three additional seats, District 23 was redrawn to include a Republican-leaning part of San Antonio. Republican Henry Bonilla won the 1992 election. And in 2003, the district was redrawn again to keep him there, by moving 100,000 Latinos out.

Bonilla was still in office in 2006, when the Supreme Court ruled that District 23 violated the Voting Rights Act. The act bars states and cities from discriminating against minority voters with crude tools like poll taxes and literacy tests (and in our time, some voter ID requirements); it also aims to ensure that when district lines are redrawn, they can’t be gerrymandered in a way that dilutes the electoral power of minorities. District 23 was supposed to be a Hispanic opportunity district—one in which Latinos could potentially elect their preferred candidate despite the racially polarized voting patterns of Anglos in the area. From ’92 on, Latinos were voting against Bonilla in greater numbers each time, nearly ousting him in 2002. But the 2003 map, the Supreme Court said, in essence “took away the Latinos' opportunity because Latinos were about to exercise it.”

And so District 23 was redrawn once again, to add an infusion of Latinos and Democrats from another slice of San Antonio. In a runoff election with Bonilla in 2006, a Democrat named Ciro Rodriguez won. (He’d previously served in Congress until his nearby district was also redrawn.)

And then in 2008, the National Republican Congressional Committee targeted District 23 for the retaking. Two years later, the party politicians who controlled the state legislature and the latest round of redistricting after the 2010 census, effectively took Rodriguez’s seat away, handing it off to Republican Francisco Canseco—a Latino, but not the candidate most Latino voters supported. That, at least, is what was implied in a decision by three federal judges in Washington, D.C., who last August rejected the new map for District 23—along with the maps for the rest of the Texas congressional delegation, and the state Senate and House. (Two of the judges are Republican appointees. The third is an Obama pick.)

As the judges tell the story, the Republicans and their mapmakers tried for a particularly sophisticated circumvention of the Voting Rights Act in District 23. They didn’t reduce the percentage of Hispanic voters—they increased it, by 0.1 percent. But along the way, in the words of the court, the line-drawers “consciously replaced many of the district’s active Hispanic voters with low-turnout Hispanic voters in an effort to strengthen the voting power of CD 23’s Anglo citizens. In other words, they sought to reduce Hispanic voters’ ability to elect without making it look like anything in CD 23 had changed.” As proof, the judges pointed to an email from the lawyer for the Texas House speaker to one of the mapmakers, urging him “to help pull the districts’ Total Hispanic Pop and Hispanic CVAPs [citizen voting age population] up to majority status, but leave the Spanish Surname and [turnout numbers] the lowest.” This would be “especially valuable in shoring up Canseco,” the email continued.

At the end of this month, the Supreme Court will hear Shelby County v. Holdera challenge to the continuing validity of Section 5, brought by the state of Alabama. It’s clear from a 2009 ruling by the justices that Section 5 is at risk. If it goes down, what will be lost—and what comes next?The District 23 saga is a classic example of the partisan misbehavior that the Voting Rights Act, and in particular a part of the law called Section 5, was enacted to stop. The Voting Rights Act is often called the “crown jewel” of civil rights law. Section 5 in particular is also “powerful and intrusive” and “controversial,” in the words of Yale law professor Heather Gerken, because it gives the Justice Department the authority to block any change in the elections process—from the location of a polling place or the hours it is open up through redistricting—in the states that Congress chose to cover back in 1965. Based on patterns of voting discrimination at the time, the list of states and cities covered by Section 5 mostly lie in the South, along with scattered counties and cities elsewhere. When Congress last renewed the act, in 2006, it left the geography of Section 5 unchanged, after hearing testimony that racially polarized voting persists in the regions covered by Section 5 more than in the rest of the country.

Read it at Slate.