On the surface, those demographic shifts may seem like good news for Democrats, since nonwhite voters are much more likely to identify as Democratic than white voters. But when we dug into how these diversifying parts of the country have actually voted, we didn’t find a uniform shift toward Democrats.2 Some suburbs that grew more racially diverse over the past decade saw a smaller swing toward Biden than others — or even moved slightly further into Trump’s column. And other suburbs that didn’t diversify much at all still became much bluer in 2020.

Rather, it was education — and particularly how much more educated a place has gotten over the past 10 years3 — that was more closely related to increased support for Biden (especially once accounting for how educated a county was in 2010). Growing racial diversity in an area was still important, since the suburban counties that saw the biggest swing toward Trump were the ones that remained less racially diverse and less educated. But the political swing among diversifying counties was much less uniform than it was in counties that became more educated.

Take Henry County, Georgia, a mostly exurban part of the Atlanta metropolitan area. Voters there narrowly backed Hillary Clinton by 4 points in 2016, but they supported Biden by a whopping 20 points this past November — a 16-point Democratic swing. What happened? Henry County was already pretty diverse, but it became even more so in the past decade. Once majority non-Hispanic white, the share of its Black population is now nearly equal to its white share. Meanwhile, the share of the population with a college degree grew slightly faster than was typical across other suburban and exurban counties. This made Henry one of the many increasingly diverse and educated counties in the Atlanta area that shifted to the left from 2016 to 2020, helping Biden become the first Democratic presidential candidate to carry the state since 1992.