Daily Kos Elections recently completed calculating the 2016 presidential election results by congressional district. With ticket-splitting rates at historic lows, and presidential results highly correlated with congressional results, these numbers serve as a strong predictor of future House election outcomes. Subsequently, the districts that saw Donald Trump improve on Mitt Romney’s 2012 margin by the greatest amount could become increasingly Republican in House races too. We’ll look at the top 25 of those seats below, all of which shifted toward Trump by at least 15 points.
As shown on the map above (see here for a larger image), nearly all of these districts are located in the Midwest and Northeast. They’re almost all monolithically white, disproportionately rural, and rank far below average in terms of the share of adults with a college degree. Those three demographics combined swung heavily Republican in 2016, even as college-educated whites voted much more Democratic compared to 2012.
Trump dominated in these seats, winning 20 of them by double digits, including six that had voted for Barack Obama in 2012. He won three more Obama districts by less than 5 points, while Clinton prevailed in just two seats. Fortunately for Democrats, they only hold eight of the districts that swung hardest toward Trump while the GOP controls 17; on the list of seats that moved most sharply toward Clinton, Republicans have much more exposure (coincidentally, also 17 seats). However, several of these Democrats only narrowly won in 2016, and if downballot trends catch up with presidential voting patterns, these eight Democrats could become even more vulnerable.
You can find a chart of all 25 districts that saw the biggest swing toward Trump below. Be sure to check out our previous maps and analysis of the presidential and congressional results for all the districts, and also our Congress guide spreadsheet, which compiles those results along with demographics and member information for every seat.
Southeastern Ohio’s 6th District saw the biggest swing to Trump of any seat, with his 43-point margin 30 points larger than Romney’s 13-percent edge. While Republican Rep. Bill Johnson had a close initial election in 2010, he won by a landslide in 2016.
Unfortunately for Democrats, they hold all four of the seats that saw the next biggest set of shifts in Trump’s favor. Pennsylvania’s 17 District, based around Scranton and Wilkes-Barre, saw Trump turn Mitt Romney’s 12-point deficit into a 10 percent victory, a change of 22 percent. Democratic Rep. Matt Cartwright won a modest victory there over an unheralded opponent in 2016, but could face a stiffer challenge in the future. Another seat in Ohio and two more in Minnesota round out the top five. See all of these districts in the chart below.