This is true. A study done found the following about polls: 1. Polls affected voters’ perceptions of the various parties’ chances of winning.2. Polls affected the vote.3. Polls affected strategic voting as some voters became less inclined to support a party whose chances of winning appeared slim.
The press and Dems know these polls that are skewed 12% for Biden are fake, but it's all part of voter suppression strategies. Source: https://www.press.umich.edu/pdf/0472099213-ch11.pdf