For all polls they publish the methodology used to determine who to survey.  Many of these polls show an oversampling of Democrats compared to Republicans.  The country appears to be divided equally between right and left. Here is one example of a methodology where they sampled 110 more democrats than republicans.  https://www.ipsos.com/sites/default/files/ct/news/documents/2020-09/2020_reuters_tracking_-_core_political_general_election_tracker_09_16_2020.pdf The polls have been wrong for 5 years.