I was reading a Hill article where it mentions one of the recent polls that had Harris ahead 4% in PA. They said only 37% of the polls respondents reported they had voted for Trump in 2020 even though he got 48.8% in PA. So there are concerns once again that Trump supporters are being under sampled.
https://thehill.com/homenews/campaign/4891637-democratic-lawmakers-worry-pollsters/