When Ronald Reagan won the White House in 1980 it was with the help of so-called Reagan Democrats, blue-collar white voters who felt the Democratic Party had abandoned them. Their over-focus-grouped, case-in-point home: Macomb County Michigan, home of disgruntled auto-workers.
Where did Donald Trump go to hold his first post-debate rally Friday morning? Macomb County.
Mr. Trump leads by massive margins in Michigan polls, and if he wins in the state on Tuesday, Macomb and the Reagan Democrats, and their sons and daughters, will be likely be at the heart of his victory. There is a strong connection between so-called Reagan Democrats and the profile of Mr. Trump's voters.
Mr. Trump's wins, so far, have been fueled by white voters with lower incomes and without a college education. In the last NBC News/Wall Street Journal poll, 61% of those who supported him did not have a bachelor's degree, compared to 39% with a degree. And Trump's voters were more likely to make less than $75,000 a year.
Those numbers match nicely with the demographic make-up of Macomb, which is less racially diverse than the country as a whole and has a lower percentage of college graduates.
And if the Trump movement is about anger at the establishment and concerns about being left behind, it has fertile ground for support in Macomb. While wages have stagnated across the country, the suburban Detroit county has been especially hard hit.
In 2000, the median household income in the county was $52,102 dollars. Nationally the average figure was $41,994. Macomb's median income was $10,108 higher.
Flash forward to 2014, the latest data available, and that edge Macomb once had is all-but-gone; the county is roughly on par with the nation. Macomb's median household income has climbed slightly to $54,059, while nationally the figure jumped to $53,482.
For the people of the county, that feels like a loss. And you can see that it is, when you adjust the numbers for inflation.
Macomb's $52,102 in income in 2000, would be worth about $72,000 today. The median household income in the county now is only $54,059, some $18,000 lower.
Nationally, stagnant wages have been a problem as well, but the difference is not as dramatic. Using national figures the 2000 median household income would be worth about $57,700 today, some $3,300 lower than the 2014 figure.
In other words, the next generation of Reagan Democrats in Macomb has even more to be unhappy about than their parents did. They missed out on the post-war boom that made Detroit a center of wealth and opportunity for blue collar Americans. The boats and summer cottages that their parents could afford are much less attainable than they once were.
That matters a lot IN Michigan because the state has a lot of "Macomb Counties" -- places once based around manufacturing that fit the same demographic profile. There are 83 counties in the state. In 61 of them 80% or more of the population is made up of non-Hispanic whites and the percentage of college graduates in under the national average.
The vast majority of those counties also have incomes below the national average.
Translation: The Reagan Democrats, and the forces that created them, are alive and well in Michigan. They are spread all around the state. That should be very good news for Mr. Trump on Tuesday as well when the primary calendar moves north to similar states.
This article first appeared on NBCNews.com.