Something a little different, a month before the election. But not too different! Though I haven’t written about it much, my interest in neighborhood and regional demographic changes extends to the political effects of those shifts. At some point, I’d really love to look at those changes within Chicago, for example in how competitive progressive candidates for alderman or mayor have been—but I haven’t yet found the data sets to really do that.

So instead, have a bigger-picture look at the shifting political allegiances of Chicago’s suburbs. All this data is from Scott Kennedy’s amazing Illinois Election Data site, from which I pulled Democratic vote shares for statewide elections (that is, everything from Comptroller to Governor, as well as federal elections like Senator and President) going back to 1990. Kennedy has this vote for four regions: the city of Chicago; suburban Cook County; the suburban collar counties (which, in this version, include everything in Chicago’s media market); and the rest of the state, which we obnoxiously call “downstate,” even though parts of it are north of the Loop.

What these lines show is how much more (or less) Democratic each of these regions were compared to the statewide vote. I did that mostly because otherwise you’d see lots of swings that aren’t about changing demographics, but just the different general level of appeal of, say, John Kerry versus Barack Obama.

As you can see, Chicago has remained pretty steady since at least 1994, at roughly 25 points more Democratic than the state as a whole. But the other regions have moved around much more.

In 1990, downstate Illinois was significantly more Democratic than either the Cook County suburbs (by about 7 points) or the collar counties (by more than 10). By 2014, it had become easily the most Republican part of the state.

Meanwhile, the Cook County suburbs were completely transformed, moving from about 7 points more Republican than the state as a whole to being 7 points more Democratic. Movement in the collar counties wasn’t as significant, and they remain much more Republican than all of Illinois, but they’ve moderated enough to become more Democratic than downstate.

This suburban shift towards Democrats is very closely linked to the rapid diversification of non-Chicago Chicagoland, both in racial and economic terms. (You can see the economic shifts quite dramatically in the maps in this post, and some of the racial shifts in this one.)

Notably, this kind of shift was not inevitable, and it hasn’t taken place everywhere. A few years ago,  the Milwaukee Journal-Sentinel published a really fantastic feature on the Milwaukee area’s political segregation—which, it turns out, is (not incidentally) just as extreme as its racial segregation. This map pretty much sums up the issue:

In 1990, and certainly 1980, Chicago’s map would have looked much more like Milwaukee’s. But our suburbs have diversified, and Milwaukee’s, seemingly, have not.

Of course, political segregation is kind of inextricable from racial and economic segregation as the raison d’etre of 20th century suburbanization and the splintering of single regions into dozens, or hundreds, of separate municipalities. As books like Crabgrass Frontier or, more straightforwardly, The Formation of American Local Governments make clear, resource hoarding—avoiding the progressive redistribution of tax money through public schools, public transportation, and so on—was a, perhaps the, major imperative for the political fragmentation of American metropolitan areas. The blurring of lines about what a suburb or city is, demographically and politically, might lead to greater regional cooperation, better resource distribution, and the end of ridiculousness like Metra, which has as much city rail infrastructure as the CTA but doesn’t do anything with it because it’s controlled by suburban officials.

Of course, a whole heap of accumulated attitudes and nonsensical, fragmented institutions makes that sort of transition a whole lot more difficult. But it’s something we might expect to hear more about as the suburbs begin to look more and more like the city.