It’s not just that. The right strongly dislikes and distrusts the media. This results in more hang ups and ignored calls. The call then goes to a more centrist R that is willing to talk. This shifts all opinion to the left and strongly taints the polling process.
Furthermore, many registered voter polls over poll young voters. They’re willing to talk, but very unwilling to vote. This also skews the left and makes them think they have much more voters than they actually have.
I just flat out lie to the posters if I have time.