The groups that swung the most to give Democrats the House

Midterm elections always draw millions fewer voters than those in presidential years, and who gained advantage in battlegrounds depends in part on who didn’t vote, as well as on those who did. On Nov. 6 that translated into an increase in relative influence for big-city suburbs and midsize metro areas. Already the largest bloc of voters in the nation and in the battlegrounds, the suburbs lost the fewest voters compared to 2016 and so gained share over both rural areas and the largest urban centers.

These graphs are based on demographic profiles and election results for almost 600 areas — counties and county portions — that make up 74 House districts that were rated competitive by Cook Political Report as of Election Day. Those races accounted for almost all of the net gains that give Democrats control of the chamber.

[Democrats projected to win control of House, but Senate remains in GOP hands]

Few groups in the battlegrounds made a swing from one party to another, but most showed a shift toward Democrats, represented here as downward sloping lines. Republicans still carried the suburbs overall, but the margin was down to less than one percentage point, and in rural areas and small towns down from double digits to five points.

Large urban counties are at the center of metros with a population of more than a million.

Suburban and midsize metros are at the center of metros with a population of 250,000 to a million.

Rural and small towns are rural areas and metros with a population of less than 250,000.

Across racial lines, Republicans won handily in areas that are more than 90 percent white, but by less than half of Trump’s margin. And in majority nonwhite areas, Democratic candidates also won by less than Hillary Clinton two years ago. Both shifts may be related to relative declines in turnout for minority as well as rural voters.

A setback for congressional Republicans was widely expected because of polling and the nation’s election history. Tuesday’s midterm was the fourth in the past quarter-century that switched power in the House to the party that had just lost a presidential race. Republicans won control of the chamber in 1994, two years after Democrat Bill Clinton’s win, and again in 2010, two years after Democrat Barack Obama’s. Democrats last won control in 2006, two years after Republican George W. Bush won his second term.

Still, the battleground shift in the direction of Democrats may be notable because it appeared to play out across blue-collar areas that surged for Trump two years ago. In battleground areas, primarily in the Midwest, where more than a fifth of workers are in factories, Republican margins slid to an average of 17 points, down from 25.

Where less than half of adults continued education beyond high school, the Republican margin dipped to 12 points from 18.

Manufacturing includes areas where at least 20 percent of workers are in the manufacturing industry.

Professional, technical, finance includes areas where at least 20 percent of workers are in information technology, telecommunications, scientific, legal, banking and related industries.