Are folks here familiar with Rachel Bitcofer’s election forecasting work? She nailed 2018, including the flip of 20 or so Romney-voting districts to the Ds. Basically, her model shows that negative partisanship caused a huge surge among D leaning independents and that the remaining surge advantage is still with the Ds. They did not “flip”. They were always D leaning, but the they showed up due to Trump. The R’s problem is that they are in permanent surge mode, with a motivated base, and they are close to maxing out. Their mid-term turn out in 2018 was actually quite good, but they got smoked in the house.
So, based on that, for 2020 she’s calling a D victory. Two caveats:
1) Bernie complicates things a bit, he may turn off some of these surge voters.
2) To really goose the surge, someone on the ballot has to be from the visibility minority community.