I fear that a fair amount of that is Republicans switching from Election Day to early voting. But let’s hope not. A lot of polling showed that there was some switching, but not nearly the majority.
https://www.pewresearch.org/politics/2024/10/24/american-voters-expectations-for-voting-this-year/
I may have posted this article one hundred times in the last week—answering the exact same question.
:-)
(not your fault if you have not seen it)