Tim, since when has a dummymander resulted from assuming the congressional vote will resemble the presidential vote, rather than from ignoring the presidential vote and assuming past congressional vote results will always remain?
Trump broke the blue wall by combining some Republican policies (opposition to immigration, discomfort with diversity) with many non-Republican policies (invest in infrastructure, no cuts to SS/Medicare/Medicaid, skeptical on trade) that put him more to the center. He swept up a lot of votes with these promises that the Congressional Rs have no interest in and he's breaking nearly all of them. After the GA-6 result, I think it's more likely that the new R voters in 2016 flip back to the Ds (or drop out of politics) than that good Clinton results in affluent districts mean 10+ Rs are going to lose their races in upscale suburban seats where Romney romped.
