Thomas Edsell writes on how immigration was a root cause issue for Trump’s victory. Those communities which went from very little diversity to a lot swung over Trump.

He writes: In Michigan, for instance, exit poll data showed that those who believe immigrants to the United States “hurt the country” voted three to one for Trump. Those who said illegal immigrants should be deported voted for Trump by better than five to one. The same pattern can be seen in exit poll data from Wisconsin, Ohio and Pennsylvania, which, while not part of the Midwest geographically, resembles it politically.

Democratic strategists were unprepared for the depth of the upheaval that shifted the balance of power across the Rust Belt.

Edsell cites these examples of communities in which immigration grew sharply and voters swung from voting Democratic to Trump. He refers to a diversity index which is a measure of race/origin diversity in a locality. Diversity indexes for some states are Michigan 42, Wisconsin 35, Ohio 36, and Pennsylvania at 41, all rank in the bottom twenty — i.e., the least diverse — of the fifty states. The diversity index for the entire country is substantially higher at 63. California 79, Nevada 73, Texas 70, and New York at 70.

Erie County, In 2012, the county backed Obama over Mitt Romney 57.1 to 41.2; four years later, Trump carried the county 48 to Hillary Clinton’s 46.4. From 2000 to 2015, the diversity index for Erie rose from 19 to 29.3. That’s a 54 percent increase, nearly double the national rate of increase, 28.6 percent.

Adams County, Wisconsin, voted for Obama over Romney by 53.9 to 45.1. Last year it backed Trump 58.9 to 37. From 2000 to 2015, the diversity index for Adams County rose from 7 to 21.3, a 204 percent increase. Macomb County, Michigan: 51.3 to 47.3 for Obama; 53.6 to 42 for Trump — its diversity index jumped from 16 in 2000 to 34.5 in 2015, a 116 percent increase.