I would add to this excellent post that the pollsters are struggling to weight their polls properly because we're completing a party re-alignment that hasn't been seen on this level in sixty years. If Harris wins this by forging a coalition of educated whites (particularly white women), black voters, and urban blue-collar unionized workers, that's a new winning coalition. She'd be winning by getting college-degree holding whites in the suburbs and black/brown/white urban voters in the same voting coalition in numbers we hadn't seen before.
And with the way Republicans are moving, it's going to be white men + poor rural and exurban whites + well-off brown immigrants (Venezuelans, Cubans) on their side vs. educated whites (especially women) + black/brown/white voters in the cities (incl. working class voters in these groups) on the Dem side.
The GOP has been working their asses off to destroy their previous advantage in the suburbs by running toward Trump. If they were smart, they'd have told the rurals to shut the fukk up and get in line with their Romney-style candidates ten years ago, softened the overt racism and made it more easily deniable, then targeted upwardly mobile black and brown Americans. Trying to hold on to the evangelical Christian population to avoid a party split was probably a mistake. Had they cut them adrift and then targeted the growing amount of high-earning women, black, and brown folks, they could have occupied the center-right and grown their party.
I think this is right, though I also see the OG poster's point. On the one hand, the move to the right on immigration was bound to happen because people very easily are convinced that immigrants are destroying the fabric of the nation, the economy, etc., etc. We need to understand that the Dems are a large tent and a lot of that tent has positions that we'd describe as "to the right," especially if we're more progressive (I consider myself to the left of most people who vote for the Democratic Party and simplify things in this way).
On the other hand, all this comes back to racism. I said it a few days ago, but you take the Trumpiest Trumper in the group, and they love social programs. If there were no black or brown folks in this country, it would have the same social systems in place as Norway or Japan. It's just that historically, and we can list example after example of this, they have consistently voted to be broke and starving to avoid black people getting a small come-up as well.
These rural Trumpers would love to exterminate black Americans because then they'd be able to go after their social programs they want with no compunctions. And that's why the wealthy present these programs as a race-focused question rather than a question of social or economic health. If these questions were presented as class-focused, and if everyone agreed that regardless of race, we're all part of a class struggle for these programs, they'd have to start contributing financially to this country that has helped uplift them and their ridiculous wealth.