538 says it has a R+0.8 House Effect
So is that (D internal) thing real or just editorializing?
The (D) or (R) marker should be based on who
sponsors the poll, not necessarily the pollster that conducts it. (This is something that annoys me about people who claim all PPP polls are D; many of them are, but not all.) In this case, the polls were sponsored by Reason to Believe PAC, whose
website describes them as "a grassroots organization dedicated to helping elect progressive Democrats in 2018 and 2020. We are not affiliated with any candidate or individual." So the (D) marker is appropriate for these.
Regarding their R+0.8 bias at 538: Change Research is a relatively new pollster, and their 538 rating is based on a very small number of polls. Unlike 538's poll database, which is constantly being updated, they update the pollster ratings very infrequently. I think the current ratings were generated in May.
