Percentage point change from

2016 to 2018 House election ◄ Swung to the left Swung to the right ►

Democrats made sizable gains in Tuesday’s elections for the U.S. House of Representatives. They won 234 seats to Republicans’ 198. Each dot on the map represents a house district, colored by the winning party. Analysis is based on results as of 5 p.m. Wednesday.

Midterm elections are often a referendum on the president’s party. While dozens of districts became more red … Arrows show House districts that voted more Republican compared with 2016.

… the overwhelming trend on Tuesday was a blue shift: 337 districts swung to the left. Arrows show House districts that voted more Democratic compared with 2016.

Only 42 of those districts actually flipped from Republican to Democratic. Most of these were in the suburbs, shown as larger dots on this map.

The districts that flipped to Democrats had an average shift of 21 percentage points. Each arrow represents a House district that flipped from Republican to Democratic and how much more Democratic it voted compared with 2016.

But the swing districts don’t tell the whole story — they represent the crest of the wave. The average district nationwide moved 10 percentage points to the left this year. Each line represents a House district and shows how much more Democratic or Republican the district voted compared with 2016, colored by the party that won the seat.

Districts where Republicans won, shown here, were caught in the wave as well — 174 of them moved to the left.

So how big was the blue wave? Over all, 2018’s shift to the left was smaller than the one in 2006, the last time the Democrats flipped the House. And it was half the size of the most recent Republican wave in 2010 when districts shifted more than 19 points to the right.