See the charts below from a good Wall Street Journal article and a new report by Dante Chinni of the American Communities Project. Links are provided and here is an important point from Greg Sargent's article on the Chinni report:
"One key finding from the study is that Biden took support away from Trump in two particular types of geographical areas: “middle suburbs” and “exurbs.”
The American Communities Project divides U.S. communities into 15 different types. In its lexicon, middle suburbs tend to be blue-collar, less affluent and less educated than the country as a whole. Many are concentrated in the industrial Midwest. They are overwhelmingly White and less diverse than more cosmopolitan “urban suburbs.” Middle suburbs are largely old-line “White flight”-type suburbs.
Trump carried the middle suburbs by unexpectedly large margins in 2016 — a key reason he flipped Michigan, Pennsylvania and Wisconsin. If Trump had anyone in mind when referring fondly to suburban housewives whose support he expected to galvanize with racial demagoguery, they’d be in middle suburbs.
But in 2020, according to the new study, Biden improved by more than two percentage points in relation to Hillary Clinton’s performance in the middle suburbs. That might not sound like a lot, but it added up on the margins, and probably helped Biden rebuild the “blue wall.”
“These should be the stronghold for Trump Republicanism,” Dante Chinni, the director of the American Communities Project, told me. “He still won them, but not by enough.”
For instance, Chinni notes, Trump underperformed in numerous key middle suburbs, falling behind his 2016 margins by around four points or a bit less in places such as Macomb County in Michigan, Winnebago in Wisconsin and York in Pennsylvania.
Chinni cited a variety of possible reasons for this. Biden (who sometimes exudes the aura of being trapped in footage of 1950s and 1960s suburban life) was well-suited to these areas. Trump’s conduct alienated people in them. And Trump never delivered on the economy, in places where he’d promised a quick fix to people who have seen the industrial base erode under them for many years.
“They’ve been burned,” Chinni told me. “He said it would get better and it didn’t.”