Obama-Obama-Trump pivot counties in 2018 U.S. House elections

There are 206 pivot counties in the country: those that voted for Barack Obama (D) in both 2008 and 2012 and Donald Trump (R) in 2016.
What happened in those counties in the 2018 elections for the U.S. House?
Democratic U.S. House candidates won 113 (55 percent) pivot counties and Republican candidates won 93.
Overall, Democratic candidates won by an average 12.3 percent margin while Republican candidates won their counties by an average 10.1 percent margin.
In counties won by a Democrat, the Republican candidate’s share of the vote was an average 21 percentage points lower than Trump’s in 2016. In counties where a Republican candidate won, their share of the vote was an average 6.9 percentage points lower than Trump’s in 2016.
Twelve congressional districts that intersect with a pivot county changed party control in 2018: 10 from Republican to Democratic, and two from Democratic to Republican.
Those districts were…
  • Republican to Democrat: FL-26, IA-1, IA-3, ME-2, MN-2, NJ-2, NM-2, NY-19, NY-22, SC-1.
  • Democrat to Republican: MN-1, MN-8.
 Across all 435 districts, Republicans lost a net of 40 of their 235 seats (17 percent). In the 203 districts that contain pivot counties, Republicans lost a net of eight of their 66 seats (12 percent).