Rich Baris is a pollster many on here need to follow. He pols scientifically and not to get the result he wants. Him and Robert Barnes talk about methodology and mistakes pollsters are using to get the Kamala bump. He goes into new voter registration and people flipping their party affiliation.
For instance.... Dems aren't doing voter drives in PA anymore because they found out they were more likely to register a Trump voter than a Biden/Harris voter. Stuff like that makes it obvious how skewed the polls are. He also goes into the scenario VHcat mentioned about voters in an apartment building and someone harvesting all those votes in one hour..... They can't be sure that those apartments are 99% dem anymore. Trump is polling better and better with Hispanics and black men.
Pubs have lapped dems in voter registration since 2020 in PA. People that think Kamala is out pacing Joe in '20 are insane. They just need it to be close enough to harvest "votes" in Philly.