This article is from the archive of our partner National Journal

You cannot stem the tide, but directing its flow is always an option. That's the lesson of the modest demographic shifts resulting from the latest round of congressional redistricting. Minority populations, which surged across the nation over the last decade, appear to be more concentrated in fewer House districts under the new maps, a National Journal analysis found.

Previous NJ studies of the "march of diversity" found minority growth to be both deep — especially in fast-growing regions of the country — and broad, affecting most areas nationwide. Since 1980, the number of majority-minority congressional districts has tripled to 106, mostly concentrated in the Sun Belt. But minority populations also swelled beyond those heavily concentrated regions. After the 1990 census and redistricting, 109 House seats had minority populations at or above 30 percent. By 2010, a majority of districts — 222 — had nonwhite populations over that threshold.

National Journal

In the 33 states that made new district demographics available, minority influence has been packed into a greater number of more heavily nonwhite districts, and the number of more heavily white House seats has also grown. Before redistricting, 67 districts fell in a diverse middle ground: more than 40 percent nonwhite, but also with sizable white populations of at least that size. Under new congressional lines, however, the middle has thinned. Across those 33 states, five additional House seats are more than 60 percent nonwhite, while the ranks of districts at least 60 percent white has also grown by eight. The middle ground lost nine seats.

North Carolina, for example, had three seats under its old congressional lines that were over 40 percent nonwhite but not quite majority-minority. The state's new map has no districts in that range; all of North Carolina's majority-white seats are less than 37 percent minority now. Instead, state legislators boosted the nonwhite population in two existing majority-minority seats and created one in the Raleigh area.

New York followed a similar pattern. Before redistricting, four majority-white districts (including three from around New York City) had minority populations pressing up against the 50 percent barrier. New York did not gain any new majority-minority seats, but the minority percentages in the white-dominated districts all fell below 39 percent, as the District Court that drew New York's map boosted nonwhite populations in the nine New York City region majority-minority seats.

In one sense, the trend dilutes minority voting power by giving those populations fewer districts to influence with their ballots. But amplifying the depth of minority influence in select areas is one of the key goals of the Voting Rights Act. Districts with high enough minority concentration allow those groups to not only influence elections but to pick their "candidate of choice," ensuring the presence of minority representation in Congress.

To construct districts with that saturation level of minority voters, mapmakers necessarily have to pick and choose nonwhite blocs from existing districts in the middle, melting-pot range of seats that shrank this redistricting cycle. Adjusting district lines codifies concentrations that developed with population growth, but it also saps other districts of their diversity.

"You have to take them from somewhere," says Antonio Gonzalez, the president of the Southwest Voter Registration Education Project, a Latino voter-participation group. Yet the diversity gap created by that process isn't lasting, thanks to rapid minority population growth. "By mid-decade or so, you have that diversity throughout districts again," Gonzalez says. "And then redistricting again."

That is how seats like California's 41st District have sprung into being. The Riverside-based, majority-Latino seat is drawn from territory that previously formed parts of three Republican districts, those of Reps. Ken Calvert, Mary Bono Mack, and Darrell Issa. All three seats were majority-white after the 2000 census and redistricting cycle, but by 2010, after a decade of rapid Latino and Asian population growth, each district had flipped.

After combining minority-heavy slices of each old seat into the new 41st District, California's redistricting commission crafted a 70 percent-plus minority congressional seat — a minority-supermajority district that could elect a minority Democrat, Mark Takano, in November. However, this development came at the cost of greater diversity in Issa's new district, which will be more than 60 percent white, the third-highest proportion in Southern California.

"This question always comes up," Gonzalez says. "Is it better to have districts you control and elect a candidate you select? Or, is it better to have your voters sort of spread around a lot of places where you're not the deciding force in electing the candidate, but you have breadth of influence? The overwhelming choice is the former: We'll take selecting the candidate."

Yet the gift of selecting a "candidate of choice" comes at a cost to the party that most minorities support. Even during historic losses in 2010, House Democrats still drew 89 percent of the African-American vote, 60 percent of the Hispanic vote, and 58 percent of the Asian vote. Concentrating those votes leaves fewer to support like-minded, but usually white, candidates in other districts.

As long as racially polarized voting persists and minorities have to rely on their own ranks to elect minority members to Congress, this paradox will persist as well. Diversity may march on, but the latest round of redistricting concentrated its influence. 

This article is from the archive of our partner National Journal.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.