By Wendy Underhill

Interested in partisan control of states? You’ve probably seen NCSL’s partisan composition map that shows states where both legislative chambers are held by Democrats in blue, both by Republicans in red, and those with split legislatures in yellow. Or, you may look at our table of legislative and state control by party, that gives the numbers of legislators of each political stripe.

Now NCSL is pleased to provide maps that show the partisan control of each district, one map for Senates and one for lower chambers—Houses and Assemblies.  We can do so through a partnership with Quorum, a Washington, D.C.-based firm that offers bill tracking and political information using data analytics.

The first thing you’ll notice is just how red the nation appears. That’s because the map is based on district lines, which represent geography and not population. Within individual states, legislative districts all have very close to the same number of people of course, but they can and do cover vastly different terrain. That means rural districts are physically larger than the pinpricks of urban districts, but both have similar populations. Or, riffing on the stickers on our rearview mirrors, “Urban districts are larger than they appear.”

Which means the colors on our new maps can be misleading from a political power perspective. Look at Nevada—it appears to be all red. Is that a mistake, given that both legislative chambers flipped to the D side in November? No, no mistake. With a close look, you can see a dot of blue where Las Vegas sits, and at higher resolution a smaller blue dot shows up for Reno. Most Nevadans live in those urban centers, and their districts are small in terms of square miles; the rest live in sparsely populated areas, so their districts are giant-sized.

Or, look at Alaska, where the Legislature is firmly held by Republicans. The map is well over half-blue. How come? That blue section is open terrain, with few communities. And yet the people who call this area home seem to favor Democrats.

The story of the map, then, isn’t that rural areas mostly vote red even though on balance that is true, as much as people tend to live in communities where the political climate mirrors their own beliefs. Crossover between people of different political persuasions comes in the suburbs, and these maps can't represent that mix because suburbs are relatively densely populated, too.

Does the redness of this map matter? Not in terms of creating public policy. For that, what matters is number of votes—and those are distributed by population, not by geography.

Note: Areas marked in gray show districts held by legislators who are neither Ds nor Rs, vacancies, and Nebraska's unicameral, nonpartisan legislature.

Wendy Underhill directs NCSL’s Elections and Redistricting program.

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