The collapse of split-ticket outcomes is a stark sign that partisan polarization has grown ever stronger over the last 30 years as America’s two major parties have sorted themselves into ideologically distinct camps. Decades ago, the way a district voted for president wasn’t a strong indicator of how it would vote for House in the same election, but the two types of elections are now very closely correlated.
This decline in ticket splitting has major implications for the way House elections work. These 16 crossover districts now represent some of the most obvious targets for each party as they attempt to gain seats in the next election, though redistricting will scramble the picture in some cases. Furthermore, it makes gerrymanders more potent and easier to draw when voters reliably back the same party for House as they do for president.
Demographically, these crossover districts share some commonalities. Democratic-held crossover districts tend to be those where Trump performed better than Mitt Romney did eight years ago and have a relatively high proportion of white voters who lack a college degree; this pattern was similar four years ago. Republican-held crossover districts have opposite characteristics and are typically suburban seats with high educational attainment levels that caused them to lurch away from the GOP over the last eight years; this pattern was also present among the GOP-held crossover districts after the 2016 election.
In addition to the traditional map above, we have also created a cartogram below that shows every district as the same size so that dense urban districts aren’t obscured and rural districts aren’t over-emphasized (with a larger version here):
The chart below, meanwhile, tells us who actually represents each of these districts, along with the results of the 2020 House election, the 2020 and 2016 presidential elections, and a comparison of the 2020 House and presidential results in each district (a larger version is here):
Following the presidential election in 2016, six of these districts were not on the split-ticket list: Iowa’s 3rd, Maine’s 2nd, Michigan’s 8th, Nebraska’s 2nd, New Jersey’s 3rd, and Texas’ 24th all went for Trump and House Republicans. The remaining 10 districts all held to the same pattern they still do now, though the four California districts plus Florida’s 27th briefly exited crossover status after the 2018 midterms when Democrats flipped each of them (Republicans won them all back in 2020).
You can find the election results for House and president for every district in our 117th Congress guide spreadsheet, along with a whole host of other demographic statistics on both the districts and the members who represent them.