How about the polls that compare voter support for Biden as compared with voter support for Senate candidates? In those battleground states holding Senate races, Biden does consistently worse than the Democratic Senate candidates. (Linked post showing the numbers and cited sources, below.)
If we want to disregard ‘Biden v Trump’ polls, I guess we can. But it would still be worth asking why Biden was doing so much better at this same time in 2020 against Trump than he is now. If polls are unreliable, shouldn’t the numbers from 2020 and 2024 be about the same? (In other words, if a bias is there in 2024, why wasn’t it there in 2020? It doesn’t appear that the tech involved, such as landlines versus cellphones, has changed in that time.)
2020 v 2024:
[post 418 in this thread–I may not be able to link due to the software:
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Senate v Presidential polling in battleground states: