Other polling has shown a slightly bigger shift among white voters in her direction (compared to Biden) than among minorities. It goes against the received wisdom but has been a persistent feature of the polls.
The place where the polls have matched the received wisdom is by age. Here her gains skew entirely young. But she hasn't lost ground relative to Biden among older voters.
A lot of older white voters appear open to voting for her.
I think it’s an open secret that the right candidate and message can be effective on the type of white voter that sprinted right with Trump. The thing about the working class is most people don’t really give a damn about the culture wars when they step into the voting booth. So whichever candidate does a better job of focusing on the people will drive that group toward them. I don’t think Hillary Clinton or Biden were effective at this. Obama and Bill Clinton were. We’ll see over the next month or so if Harris is.