That’s what they did in AZ in 22. They even sabotaged the voting machines in the R districts to do it.
And if Trump is more than 10 points ahead, they'll just keep 'counting' cheat-by-mail-in ballots until enough are found to put Biden ahead. There is no fraud margin for the mail-ins. There is no time-limit on when 'counting' must stop.
At this particular point in time, we can see large changes in the same poll’s results. This is the time period when methodology changes are made. Maybe a change in Likely Voter definition (maybe a change of self-reporting of Likely To Vote, vs voted in the last X elections).
The biggest difference among polls I have see is how weighting is determined. Some polls use turnout in recent elections to determine what R/D/I mix to seek in their surveys and some polls are using the Census (which we know was corrupted for funding).
So wait a month or two before you start comparing a given poll to its previous measurement.