An anonymous professional pollster let the cat out of the bag about how they jimmy the national polls to always show Biden ahead of Trump. He didn't mean for it to go public but it got out anyway. It has to do with sampling the subgroups.

Among the republicans Trump is weakest with suburban republican women. So they over sample that group.

Among the Democrats Trump is strongest with the rural "Reagan Democrat" types. So they under sample that group.

And voila!! Biden always wins the polls.

But you are going to see a different story come election day.