How suburban voters could alter the House on Tuesday and the White House in 2020

The political gap between Republican rural areas and Democratic urban areas is widening. Suburban voters, hanging near the middle, shift back and forth across the divide. These turns can appear subtle, but they can steer the politics of the nation.

National divide in presidential elections

Percentage-point margin

R+30

R+27

Rural and

small towns

More

GOP

R+1

Suburban/

midsize metro

0

More

Dem

D+30

D+32

Big urban

’04

’08

’12

’16

The suburbs and midsize metro areas are poised to make an impact Tuesday. Because they have the largest numbers of voters, even a shift that looks unremarkable in percentage points can yield a decisive margin in votes.

Big-city suburbs and similar midsize metros together make up the biggest bloc in more than half of the competitive congressional districts on Tuesday’s ballots. And in another handful of districts that comprise all three kinds of areas — Big urban, Suburban/midsize metro, and Rural and small towns — the suburbs have enough voters to swing the balance.

That gives suburbs an outsize role in deciding the 73 competitive House districts, all but four held by Republicans. Democrats would need a net gain of 23 seats to win control of the chamber.

The map above is based on an analysis of counties and parts of counties that make up the House districts rated competitive by the Cook Political Report (as of Oct. 30). Big urban counties are at the center of metros with population of more than a million. Suburban/midsize metros includes the suburbs of those big urban counties and metro areas with 250,000 to 1 million people. Rural and small towns is a group that takes in rural counties and counties in metros of less than 250,000 population. (Alaska, with a statewide competitive House race, is not included in the analysis.)

Pennsylvania, one of the key swing states in the 2016 presidential election, shows how the suburbs can be deciders. A Republican surge netted Donald Trump a 439,000-vote lead in the state’s rural areas and small towns. While that was far better than Republican Mitt Romney’s showing there in 2012, it wasn’t enough on its own to beat Democrat Hillary Clinton, who amassed 580,000 votes in Democrats’ urban strongholds of Philadelphia and Pittsburgh.

What made the difference in the end was a Republican shift across much of the state’s suburbs. Those areas overall broke from a near-tie going to Barack Obama in 2012 to a Republican advantage in 2016 that was large enough to carry Trump to a statewide victory of less than one percentage point.

A similar suburban swing powered Trump’s one-percentage-point victory in Florida, a win that, together with Pennsylvania’s, sealed an electoral majority. Suburban voters also had the potential to be decisive in other swing states such as Michigan, Ohio and North Carolina because they were the largest voting blocs.

So the drama of Tuesday’s election begins with whether Republicans can keep their hold on the House. Looking ahead, the question is whether any shifts, especially in the suburbs, would be a temporary retreat from 2016 or persist into 2020.

It’s not unusual for midterm House elections to set back the party in the White House. Also, this year's battlegrounds may not be typical, because income, education and diversity in contested districts are generally higher than U.S. averages. In the battleground suburbs, for example, the typical income of $71,600 is almost 20 percent higher than the nation’s suburban average. Still, there are signs that next week’s House races may be closer than the Trump-Clinton numbers, perhaps in surprising ways.

Results of a Washington Post-Schar School poll across battleground districts suggest that Democrats still hold an advantage in big urban centers but one not as lopsided as in the presidential race two years ago. About 51 percent of respondents supported Democratic candidates in their House district, and 44 percent supported Republicans.

The poll found Democrats with a close advantage of 49 percent to 46 percent across suburbs, where Trump had won by about five percentage points. And in rural areas and small towns, where Trump won overwhelmingly, House Democratic and Republican candidates were tied 48 to 48.

Special elections are uncertain examples because their environment is so out of the ordinary, but one in Pennsylvania’s old 18th District also showed a Democratic shift. In April, Democrat Conor Lamb eked out a 0.3-point win where Trump had won by 20. Lamb’s win was powered by a Democratic surge in urban precincts on the west side of Pittsburgh. Republican margins dropped by double digits from Trump’s share, across suburbs with a history of auto-plant closings and rural coal-mining communities. In Ohio’s 12th District, Republican Troy Balderson won less by than a percentage point where Trump had won by more than 10.

Trump won in 50, or more than two-thirds, of the House districts now being contested. But in the last week of campaigning, his appearances are focusing mostly on statewide governor and U.S. Senate races, and the scheduled visits are mostly to areas with House races rated as solidly Republican, not competitive. That goes for Fort Myers, Fla.; Columbia, Mo.; Chattanooga, Tenn.; and Macon, Ga. From Indianapolis, the nearest competitive House district will be 150 miles away, and from Pensacola, Fla., 300.