In recent history, Democrats typically improve on their popular vote margin from a midterm election to the subsequent presidential election in the House of Representatives, regardless of whether the incumbent is a Republican or a Democrat.
1994 to 1996: R+6.8% to D+0.1% (D+6.9% improvement)
1998 to 2000: R+1.1% to R+0.5% (D+0.6% improvement)
2002 to 2004: R+4.8% to R+2.6% (D+2.2% improvement)
2006 to 2008: D+8.0% to D+10.6% (D+2.6% improvement)
2010 to 2012: R+6.8% to D+1.2% (D+8.0% improvement)
2014 to 2016: R+5.7% to R+1.1% (D+4.6% improvement)
From 1996 to 2016, Democrats do, on average, 4.2% better in House elections during a presidential year than the House election two years prior.
Given that the 2018 House popular vote margin was D+8.6%, one might have expected the 2020 House popular vote margin to be D+12.8% based on previous data. However, the actual 2020 House popular vote margin was D+3.1%, which is 9.7% more Republican than what recent trends indicate. 2020 was the first presidential year since 1992 in which Republicans improved their popular vote margins in the House of Representatives from the last midterm election.
What is this supposed to mean? Was this just a fluke, or is this really troublesome for Democrats?
The Democrats, as a whole, have taken uniformily Far-Left positions on a wide range of social issues. They are far more socially liberal than the entirety of their party. Younger voters are more in line with the Democrats, to be sure, but younger voters don't always enter the electorate at the same rate as older voters depart the electorate due to death or change of partisan leanings in its older voters.
