This entire election cycle we’ve heard (and even written) that the Democrats’ path to a House majority may lie in the suburbs. Although that summary is a bit simplistic because of the breadth of the House battlefield, an analysis of a recent article from CityLab and FiveThirtyEight’s House forecast suggest that Democrats’ gains will come from districts that are more suburban than not.

CityLab placed all 435 House districts into six categories based on neighborhood density, two of which are predominantly suburban: “Sparse Suburban” and “Dense Suburban.” The former are districts that have a mix of exurban development and outer-ring suburbs at the periphery of major metropolitan areas like the Michigan 11th or New Jersey 3rd. And the latter are districts composed of more inner-ring suburbs and some urban areas, like the California 10th and Utah 4th. Together, these two categories have 169 districts, which means they make up 39 percent of all House districts. This compares to 42 percent of districts that are more rural and 19 percent that are more urban.





FiveThirtyEight Senate forecast update for Nov. 1, 2018

Interested in knowing the likelihood that these districts will deliver a win for Democrats (or help Republicans keep control) in the midterms, I used the Classic version of FiveThirtyEight’s House forecast to understand the odds in these 169 districts. And what I found is that districts that are predominantly suburban could almost give Democrats a majority on their own.

Here’s my reasoning: Democrats currently have about a 6 in 7 (or 86 percent) shot of winning a House majority, and if we treat every district where a Democrat is favored, even slightly, as a win for that party, Democrats would gain a net of 32 seats. And 21 (or around 60 percent) fall in either the “Sparse Suburban” or “Dense Suburban” categories. Yes, these 21 seats are still shy of the 23 that Democrats need to win a majority, but they could play an important part in the party’s strategy to take back the House. (One important caveat: This seat count does include five toss-up districts. They’re toss-ups where the Democratic candidate is slightly favored to win, but they’re still toss-ups.)

Democrats could be rockin’ the suburbs The types of districts where FiveThirtyEight’s House forecast gives Democrats an edge to pick up seats, as of Oct. 31 Current districts Forecasted districts district category Dem gop Dem gop Dem. pickups Share of dem. pickups Sparse Suburban 35 51 48 38 D+13 41% Dense Suburban 56 27 64 19 D+8 25 Urban-Suburban 41 7 47 1 D+6 19 Rural-Suburban 21 93 24 90 D+3 9 Pure Rural 9 61 11 59 D+2 6 Pure Urban 33 1 33 1 0 0 Total 195 240 227 208 D+32 100 Data based on individual district win probabilities, which differs from the overall forecast. Some columns may not add up due to rounding. Data as of 2 p.m. Eastern on Oct. 31, 2018. Source: CityLab

But it’s not just these two mostly suburban categories where Democrats could pick up seats. Two of the other four CityLab categories also contain districts that are somewhat suburban and could be pickups for Democrats. We’re talking about places like the Florida 27th — a mix of urban areas with some denser suburbs — and the Kentucky 6th — suburban and rural with little or no urban area — that respectively fall into the “Urban-Suburban Mix” and “Rural-Suburban Mix” groups. Together, they make up 37 percent of House districts, and if we combine them with the two predominantly suburban categories, you could say that almost every district where Democrats are favored to make gains has notable suburban characteristics, with just three potential pickups coming from “Pure Rural” seats. (Note: The oft-discussed Obama-Trump and Romney-Clinton districts both overlap with these suburban categories.)

Also, while Democrats are struggling to make significant gains in more rural parts of the country, you can see their potential in urban areas is practically maxed out, making their drive to pick up suburban seats all the more pressing.

But what does this mean for Democratic representation? Democrats already control 56 of the 83 “Dense Suburban” seats, so their potential gains in districts such as the California 49th and the Arizona 2nd — two GOP-held seats where Democrats have better than 9 in 10 odds of winning — would only make this Democratic-leaning category bluer. Rather, the potential for major Democratic gains is in the “Sparse Suburban” category. Such gains would dramatically shift the Democratic share of “Sparse Suburban” seats, from around 2 in 5 currently to potentially almost 3 in 5 after the midterms, essentially flipping the party makeup of this group and making it the group with the largest forecasted swing among the six CityLab categories.

Where each party dominates Current share of districts controlled by Democrats in each neighborhood density category and share Democrats are forecasted to control in 2019 Share of Democrat-held districts district category Current Forecasted Difference Sparse Suburban 41% 56% +15 Urban-Suburban 85 98 +13 Dense Suburban 67 77 +10 Pure Rural 13 16 +3 Rural-Suburban 18 21 +3 Pure Urban 97 97 0 Total 45 52 +7 Data based on individual district win probabilities, which differs from the overall forecast. Data as of 2 p.m. Eastern on Oct. 31, 2018. Source: CityLab

Where this change might be felt most is in Pennsylvania — thanks in large part to court-ordered redistricting. Democrats are solid favorites to capture the 6th, 7th, and 17th districts, all part of the “Sparse Suburban” category. But it’s not just Pennsylvania where Democrats stand to gain ground. The outer edges of metropolitan areas such as Minneapolis-St. Paul (the Minnesota 2nd and 3rd), New York City (the New Jersey 7th and 11th), and Washington, D.C., (the Virginia 10th) are also “Sparse Suburban” areas represented by Republicans but featuring races that favor Democrats to some degree. Democrats could also make gains in the “Urban-Suburban” category, although they already control the vast majority (85 percent) of those seats. But if each party wins every seat where they currently have an edge, Republicans will find themselves holding the majority of seats in just two of the six categories, both of which are predominantly rural: “Rural-Suburban” and “Pure Rural.”

Combining our forecast with CityLab’s data suggests that the GOP, which already does best in rural areas (see the current party breakdown in our first table), would become more concentrated in those places. Currently, Republicans control 80 percent or more of the seats in each of the two rural categories. And our Classic forecast does not expect dramatic Democratic gains there. On the other hand, the predominantly suburban districts — “Dense” and “Sparse” — could undergo a large shift whereby Democrats go from controlling 54 percent of those seats to holding 66 percent.

The battle for control of the House will mostly play out in suburban swing districts, as these are the districts most likely to change hands and there are enough of them to give Democrats much of what they need to take back the House.