According to the Daily Kos’s presidential tally by Congressional district Donald Trump likely carried a majority of the nation’s Congressional districts (just like Romney). He also is likely to have carried 12 districts currently represented by Democrats. While this will give the GOP plenty of opportunities come the year after next Democrats also have quite a few seats they could eye.
Clinton carried a whopping 23 districts represented by Republicans. Notably, seven of them are located in the liberal bastion of California and three in the red state of Texas. Due to the daunting Senate map the party faces in 18 their best chances for gains are in the House (gerrymandering complaints or not).
Despite the math and number of opportunities, Democrats will face formidable obstacles in their bids to take these seats. First-off, the strength of GOP incumbents is partly why the party held so firm in California. These incumbents are likely to stay for the most part which means Democrats would need to pick off Cuban-American icons in Florida, Barbara Comstock in NoVA and Mike Coffman in the Denver suburbs.
Secondly, Democrats will be running against history. In 2006, the last time Democrats made midterm gains in Congress, they relied on the support of almost a majority of whites. Today, Democrats would be lucky to get 2/5 of the white vote meaning they need their majority-minority coalition to turn out. Yet, since Obama won election in 2008, this coalition has failed to turn out in three of the last four contests. Even a GOP downturn in the midterms might not be enough to shatter their House majority if Democrats don’t turn out in force.
Finally, Democrats will be playing defense in some blue-collar districts in Pennsylvania, Minnesota and Iowa. Republicans could steal a few ancestrally blue seats in these states and make the party’s path to the majority tougher.
That said, despite the unpopularity of Trump and strength of GOP incumbents there is historical evidence to suggest Democrats are primed to make major gains in the midterms. I’ll use the West as an example.
Since 1988, Democrats have realized major gains in urban areas. In the West in particular, this has been realized in California and Colorado. It’s why suburban Colorado has flipped to blue at the Presidential level and why SoCal’s Orange County is now purple. The larger the share of the urban vote the better it is for the Democratic Party. The same can be seen here for Virginia and NoVA.
Thus, the real question is just what role did Trump play in these district’s votes in 16 and what role will he play in 18? Were these split district voters preferences more about not being able to stomach Trump? Or was it that these voters were starting to realign their partisan preferences?
We will start with the first question. This is obviously the more difficult question to answer considering we only have election returns to go on. But, we do know that education correlated quite clearly with vote preference in this election and many Clinton/Republican districts were better educated than the nation.
The second question is slightly easier to answer because we have more data points. Specifically, county and state-wide election results. Short of Presidential election results, the majority of Romney districts and precincts stuck with their Republican Congressman/woman (and Senate candidate). Further down-ballot, these same districts and precincts voted for GOP legislatures.
Now, it is possible that 2016 has similarities to 1968. That year, Richard Nixon’s vaunted Southern Strategy worked but it did not translate down-ballot. Democrats would hold legislatures and governorships in the South well into the 21st century.
Clinton’s success last year could herald the same thing. The beginning of a change. However, if 1968 is any guide, this change will take quite a bit of time to manifest itself in a way to benefit the party and certainly not quickly enough for 2018.
This leaves Democrats relying on a Trump Presidency that divides the nation, depresses traditional GOP turnout and gives Democrats numerous pick-up opportunities. It is certainly possible this could happen. But, Senatorial and gubernatorial contests promise to swallow up much needed dollars for Democratic challengers. So, even with all the opportunities the party has, they will still be running against entrenched incumbents amid an electorate that might not like Trump but likes their representative/s.