Voters cast their ballots at in Greencastle, Pa., in Tuesday's primary election for that state. (Colleen McGrath/Public Opinion/AP)

Control of the House of Representatives is going to be decided this November in a relatively small handful of races across the country, some 70 out of 435 House districts.

New data show that although spread out, these districts encompass a narrow slice of America. The voters who could decide control of Congress tend to be whiter, older and more educated than the rest of the country.

That's according to census data analyzed by Quorum, a software start-up that builds tools for public affairs professionals.

They found that these 72 swing districts are 48 percent less black than the average congressional district and that their voters are a third more likely to have some kind of higher education. Voters in these districts are also more likely to have health insurance, less likely to rely on food stamps, less likely to be in poverty and more likely to have jobs in, say, the financial sector over agriculture. They're also older on average.


The political ramifications of the split between swing districts and the rest of America isn't hard to decipher. Candidates trying to win these important races are going to tailor their messages to these older, whiter, better-educated and wealthier voters. Because there are so few competitive districts these days, the conversation in these races could drive the national political conversation, potentially away from issues the rest of America may want to talk about.

Police brutality, the opioid epidemic, health insurance, hourly wages and college affordability could all take a back seat in these races that will decide control of the House. It's a safe assumption that those aren't the highest-priority issues with the voters who will have an outsize influence on which party controls Congress.

That's not to say that these issues won't be discussed at all in any high-profile campaigns. Opioid addiction is a massive issue in some Senate races. And there are plenty of candidates on the left talking about raising the minimum wage and candidates on the right willing to talk about redoing the Affordable Care Act.

But just because many candidates for Congress are talking about these issues doesn't mean that candidates for key seats in Congress will be. There just aren't that many competitive House seats left. The Cook Political Report, which ranks districts based on their level of partisanship, has found that there are 168 strongly Democratic districts and 195 strongly Republican districts, compared with 72 that either side has a realistic chance of winning.

Analysis | Can Democrats win back the House in 2018? It’ll be tough.

Gerrymandering and self-segregation among like-minded people have contributed to a steep decline in competitive districts over the past few decades. The number of swing districts has gone down by more than 50 percent since 1994.

Today, swing districts are concentrated in suburbs of cities, such as outside Philadelphia and in Southern California and New Jersey. The demographic data that Quorum put together matches up with what most of us think of as a suburban resident: better off and even slightly disconnected, geographically and socioeconomically, from the rest of America.

As for which party has the advantage over this kind of voter, right now we give a slight edge to Democrats.

They've won some big races in 2018 in suburbs. Rep. Conor Lamb (D-Pa.) won a special election in March for a district outside Pittsburgh that President Trump won by some 20 points. Democrats painted the Virginia suburbs outside Washington blue in November in state elections — a warning to vulnerable GOP Rep. Barbara Comstock.

Plus, as a February piece in National Journal notes, Republicans have spent the past few election cycles gearing their messaging to more rural, working-class voters instead of talking to suburban families. Those rural voters helped carry Trump to the White House in 2016, but they aren't the ones who will help decide which party controls Congress in November.

Only a small slice of Americans get to do that.