If we look at all the special elections, it’s interesting to note that Democrats this year have been outperforming their 2016 baseline most in the districts where Clinton underperformed Obama and least in the districts where Clinton outperformed Obama. The latter group tends to include more highly educated, suburban areas that traditionally voted Republican. These places may be growing bluer, but perhaps Clinton did as well as could be hoped for by a Democratic candidate for the time being. In the districts where Clinton didn’t do as well as Obama had, it’s possible that traditional Democratic voters who voted for Trump in 2016 may not be voting for Republicans in 2017.