I think this might be young Nate Cohn’s best article:

“This was the core of the Obama coalition: an alliance between black voters and Northern white voters, from Mr. Obama’s first win in the 2008 Iowa caucuses to his final sprint across the so-called Midwestern Firewall states where he staked his 2012 re-election bid.

In 2016, the Obama coalition crumbled and so did the Midwestern Firewall. …

The countryside of Iowa or the industrial belt along Lake Erie is not the sort of place that people envision when they think of the Obama coalition. Yet it was an important component of his victory. …

The turnout probably increased among all major groups of voters — Hispanics, white Democrats, white Republicans — except black voters.

The conclusive data is available in the Southern states where voters indicate their race on their voter registration forms, and they point toward a considerable decline in black turnout. …”