One of the reasons that most people, at least eventually, accepted the 2020 election results is because it followed from the polls.
Compare the following two websites and you'll see what I mean. The first is a map where you can see the election results by hovering over each state. The second is a map where you can see the poll numbers in each state just before the election by clicking on each state.
See maps and real-time presidential election results for the 2020 US election.
www.cnn.com
Pay special attention to the swing states, which of course really decided the election. You will find that the results (or at least what they said were the results) match up very close to the polls taken just before the election.
Now, what I am saying is that if Trump is far enough ahead in the polls right before the election, especially in the swing states, and THEN somehow Biden still wins those states, it would not be so easy for the public to acquiesce because it would make no sense.
Just before the 2020 election, despite Biden being ahead in the polls in those states, many people felt that Trump may still win them because the polls often tended to favor the Democrat. That feeling was enhanced when Trump pulled out early leads on election night. However, when Biden suddenly surged ahead and overtook Trump (supposedly), they chalked it up to late mail-in votes, and then pointed to the polls, saying "It's just like predicted, so it makes sense."
That logic will not work if Trump is ahead in the polls this time.