One of the central goals of Data for Progress is to build tools to understand the political geography of public opinion, and one tool we use is the national-median gap. The idea is quite simple: we compare support for a policy nationally to its support in the median state (a similar standard can be used to measure gerrymandering). What the national-median gap measures is how a policy polls across the nation to how it polls in the middle-most (median) state (i.e. half of states will have lower support and half of states will have higher support).
This measure is important for Democrats to use and understand. Let’s explore a simple example. In 2012, Obama won 52 percent of the national two-party vote. In the median state, he won 52 percent of the two-party vote, producing a national-median gap of less than a percentage point. By contrast, in 2016 Clinton won 51 percent of the national two-party vote, however, in the median state Clinton won 48 percent of the vote, for a national median gap of 3 points, a gap nearly eight times larger than Obama’s (.4). That is, support for Obama was more efficiently distributed throughout the country.
In a previous blog post, we showed that Trump benefited from political geography. Here, we analyze Trump’s signature policy priority: the border wall, which we previously mapped here. We estimate support for the border wall in the median state is 3.3 percentage points higher than its national support. To put that in context, a 3.3 percentage point boost is almost the same size geographic advantage that converted Donald Trump’s popular vote loss into an electoral college win.
Not every policy will have the same advantage or disadvantage due to geography, and each policy needs to be analyzed on a case by case basis. However our preliminary analysis of a number of anti-black and anti-immigrant views suggests that such opinions benefit substantially from the structure of American politics. Given that politics in the US is determined by states, we should mentally add a bit more than three points to national polling support for the border wall. As we saw in the 2016 election, that’s often enough to make a difference. White supremacy is built into the political geography of the United States, and this helps us understand how it plays out in politics.