I don't know about the specific campaigns that you are referring to, but in my experience a lot of the information used in campaigns I've been involved in comes from previous canvassing sessions. Political parties in most countries are involved at many levels where there are elections. Canvassing doesn't just take place for the big elections.
One year they will have been round and had a lengthy discussion with Mrs X, but Mr X slammed the door in their face another time. This was somewhat lower tech: the information was printed out and attached to a clipboard.
Most of the time this information is correct. It's more interesting when it's really incorrect. That said, some of the best sessions I've been involved in were where there was no information.
Exactly. This is the old-fashioned approach to campaign targetting that Cambridge Analytica was trying (and failing) to replace: just send a bunch of volunteers to talk to them about who they're voting for and why, then put that in your big database. One of the dirty not-so-secrets about CA is that according to the Trump campaign, they were abandoned completely in favour of that old-fashioned approach because they were worse. Similarly, if you've been paying attention, you might have noticed a few insider stories about how one of the Hillary Clinton campaign's big screw-ups was underestimating the importance of that data compared to modern big data tech and basically throwing a lot of it in the trash. This didn't get nearly as much coverage as the idea that Cambridge Analytica, Trump, and Facebook were conspiring to brainwash the population, probably because it was less juicy a narrative and kind of embarassing to the Clinton campaign and the DNC.
One year they will have been round and had a lengthy discussion with Mrs X, but Mr X slammed the door in their face another time. This was somewhat lower tech: the information was printed out and attached to a clipboard.
Most of the time this information is correct. It's more interesting when it's really incorrect. That said, some of the best sessions I've been involved in were where there was no information.