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Partisan advantage by congressional delegation
In 2010, as Daily Kos readers are well aware, Republican swept to victory in Congress, taking back the House and making big gains in the Senate. At the same time, they also captured many governorships and legislatures, giving them control of the decennial redistricting process. With the map-maker's pencil firmly in hand, these new GOP majorities were able to draw district lines that favored them both at the congressional and legislative levels.
Scholars and pundits have debated exactly how much these maps are tilted in the Republicans' favor, but at Daily Kos Elections, we've developed one metric that's methodologically rigorous and highly illustrative of the GOP's advantage, relying on the "median seat" in each legislative chamber or state congressional delegation. The numbers, as we will explain, are starkly in favor of the Republicans.
Previously, we calculated the results of the 2012 presidential election according to every congressional and legislative district in the nation. That allows us to determine every state's median congressional district and every chamber's median legislative seat. But what do we mean by this median seat? In state legislatures, the median seat is the theoretical halfway point in each chamber whereby, if Democrats held every seat bluer (or Republicans held every seat redder), they'd control a majority of seats in that body.
For instance, in Ohio's state House, Mitt Romney won the median seat by a 51.3 to 47.6 margin. That means that if Democrats want to retake the House under the current map, they'd need to win all the districts that suported Romney by a 3.7 percent margin or less—at a minimum. Things rarely work out so precisely, though: Since Republicans are likely to hold a few seats that are bluer than this threshold, Democrats would have to capture some redder seats as well. That's no easy task.
You can find our complete calculations for each state's median districts at this link or below the fold. (Alabama, Maryland, and Mississippi are forthcoming.) To compute the median district, we subtract Romney's percentage of the vote from Obama's in each district, and sort by the resulting margin. The middle-most district—the one where half the seats are redder and half are bluer—is the median. If a state or chamber has an even number of districts, we average the Obama and Romney percentages for the middle two seats to come up with the median.
We've also introduced an "advantage" column, to show how far to the left or right the median district is from the state as a whole. To calculate the advantage, we subtract the Obama-Romney statewide margin from the median district margin. In the Ohio House, for instance, Obama lost the median seat by 3.7 points even though he won Ohio overall by 3 points, giving Republicans a considerable 6.7 percent advantage.
Head below the fold to learn just how strong this Republican advantage is—nationwide.
Since Republicans drew most of the maps, it's unsurprising they hold an advantage in most chambers. In Congress, the GOP has a partisan advantage of some type in 31 states (ranging from a minuscule 0.01 edge in Hawaii to a massive 14.8 advantage in Georgia), compared to just 12 for Democrats. (Seven states have just a single at-large seat.) Stephen Wolf's map at the top of this post offers a state-by-state visualizations where each party holds the edge, and how deep it is.
Partisan advantage by state Senate
In the 47 state Senates we have calculated (including Nebraska's unicameral legislature), the GOP has an advantage in 39 chambers while Democrats hold the edge in a mere seven. Team Red's biggest advantage is in Georgia, where the median seat is 17.8 points to the right of the state. Democrats' largest advantage is, shockingly, in North Dakota, a state where Republicans drew the lines. But that advantage is pretty small (just 1.8 percent), and in any event, the GOP remains firmly in control of the chamber.
Partisan advantage by state House
In the lower houses of the legislature (known variously as the state House, state Assembly, or House of Delegates), the GOP has a 37 to nine edge. The GOP's biggest advantage is in Louisiana, at a massive 20.41 points to the right of the state. The Democrats' best chamber is Colorado, where the median seat is 7.9 points to the left.
It's worth noting that the GOP often has at least some advantage under maps drawn by Democrats. A major reason is that Democratic voters tend to be much more heavily concentrated in urban areas than Republicans, making it difficult to avoid packing them together. You can see this in Illinois, a state where Democrats aggressively sought to promote their interests, but where the medians in both legislative chambers are still slightly to the right of the whole state.
But the clustering of Democratic voters is only partly responsible for the sea of red you see in all the maps above. Republicans were, on the whole very crafty when it came time to draw the most recent set of lines, and it shows not just in the breadth of their advantage but its depth as well. Not only is the median seat to the right of the state in so many more states than it is to the left, but it's much further right as well. In congressional delegations that lean right, the average advantage is 6.7 percent; for those that lean left, it's just 2.1 percent.
Meanwhile, in lower chambers, it's 6.3 percent versus 2.9 percent, while in upper chambers, it's 5.8 percent versus 0.9 percent. That gives the GOP a near-hammerlock on many legislative bodies, and those are the very same bodies that will again get to redraw the congressional lines following the 2020 census. Put another way, to undo the Republican gerrymanders at the congressional level, Democrats will have to win legislative seats that have also been gerrymandered to make life as difficult as possible for the blue team.
The good news, at least, is that Democrats are well aware of this, and have already started focusing on the battle for 2020 with a new super PAC headed by Mark Schauer, a former congressman and state legislator from Michigan. But as our median seat analysis shows, winning back state legislatures—and thus unlocking the keys to Congress—will be no easy task.
Our complete chart of median districts by state is below. You can also
click here to view the full table in Google Docs.
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