From the moment Donald Trump secured the 2016 presidential nomination, throughout his Access Hollywood sexual-assault tape scandal, and even right up until today, Republican elected officials have overwhelmingly given him their full backing. There’s one incredibly important reason for why so many House Republicans in particular continue to stand by him: He carried the vast majority of the districts they represent by a very wide margin.
This fact is a crucial piece of context for why House Republicans so steadfastly support Trump even when polls show his national approval rating in the low 40s and debacles like National Security Adviser Michael Flynn’s resignation unfold almost daily. Republican members of Congress are almost all far more concerned with primary challenges than general election defeats because Trump remains almost uniformly popular both with the Republican base and with the swing voters in their districts who would put them over the top against a Democratic opponent.
Daily Kos Elections has calculated the 2016 presidential election outcome in all 435 congressional districts, which we’ve illustrated in the map at the top of this post that renders each district the same size. It reveals which party won each seat at both the presidential and congressional level (see here for a larger image or a traditional map). House Republicans won 241 seats in 2016, and Trump won 218 of those, meaning an outright majority of the House consists of Republicans in Trump districts. And in most of those 218 seats, Trump won handily, as we’ll explain further below.
The chart below, known as a histogram, graphs every Republican-won House district according to its 2016 presidential election margin. Trump carried half of the Republican-won seats by almost a 20-point margin or greater—all those to the right of the line marked “Median District”—and he bested Clinton by at least 10 points in 179 Republican-held seats, or roughly three-fourths of the GOP caucus. So even if Trump’s approval rating is in the low 40s nationally, there’s a good bet it’s higher in these types of districts.
These numbers are so important for a general election context because the presidential and congressional outcomes were extremely correlated with each other in 2016 and recent elections. As this scatter plot below demonstrates, relatively few races (those farthest away from the diagonal line) saw a meaningful divergence between the presidential results and the House results.
Trump won’t be on the ballot in 2018, but as the most visible political figure in the country, he’ll be on nearly every voter’s mind. Presidential approval ratings have long proven a critical factor in determining how the president’s party does in congressional elections. That’s especially true in the last few decades, when partisan polarization has reached highs not seen in many generations, meaning that fewer voters are apt to split their tickets. Republicans in districts that Clinton won might be inclined to shun Trump with his approval ratings as low as they are, but there simply aren’t many of them—just 23 overall.
And polarization cuts two ways. Republicans who tether themselves to Trump in districts that Clinton easily won might cost themselves victory in the general election. However, if they staunchly oppose Trump in a district that voted for him in a landslide, they could likewise go down to defeat, just this time in a primary. While Republican base voters might be willing to tolerate apostasies in a tough-to-win district, they know they don’t have to do so in one-sided districts. Alabama’s ruby-red 2nd District was a prime example of this phenomenon in 2016.
This Montgomery-area seat supported Trump by an enormous 65-33 spread last fall, and GOP Rep. Martha Roby had faced only token Democratic opposition and easily won re-election in 2012 and 2014 by roughly as much as Trump carried the district. However, following his sex-assault tape scandal, Roby became one of the very few red-district Republicans to disavow Trump’s candidacy. That sparked a last-minute write-in bid from a furious Trump supporter, who won 9 percent and held Roby to a relatively weak 49-41 victory over an unheralded Democrat despite Trump’s far larger landslide there. The congresswoman could now face a serious primary challenge in 2018.
One of the first and foremost concerns going through any congressmember’s mind is how political actions will affect their chances of winning re-election. Of course, legislators also care about preserving their party’s overall majority and achieving potentially unpopular major policy goals, even if pursuing one of those two goals can hurt their chances of re-election in a primary or a general, respectively.
However, the vast majority of House Republicans have far more to fear from angering their Trump-supporting base voters ahead of primaries 12 months from now than they do from a general election defeat to a Democrat in 20 months. Trump might have to become a whole lot less popular or more dangerous for those considerations to change.
