“I think they have lists of pre-screened poll participants in their databases and are able to pull a scientific sample online from known participants. In these days, they might be more able to obtain a sufficient number of responses from a balanced demographic than firms still relying on telephone contact.”
For two presidential campaigns, Bush II’s, I was on two pre-screened polling companies’s lists.
I knew that I would be called and what the questions were before the polling calls. They called ahead re the date and time and the questions.
We have a couple of younger relatives without landlines, and they are contacted via their cell phones by legit pollsters.
And also with the information in post #90, it sounds like firms are adapting to the internet and cell phones and using a mix of ways to poll their respondents.
I was once called by Pew Research and answered pre-screening questions, but I guess I didn't fit the needed demographic because I wasn't called to participate in any polls.