Strictly anecdotal, but growing up in Lake County, Indiana and being involved in the local Democratic Party, the ones I met were of all ages but generally seemed to come from union families and many were ethnic whites (Poles and Greeks, especially) who kept the culture.
Three were white girls from my high school who were in relationships with/married to nonwhite men. Meanwhile, the local Dem Party was 50/50 noncollege whites (virtually all older) vs. college whites (lots of lawyers!) + minorities.
Again, strictly anecdotal.
Interesting about the local Dem party. I guess it makes sense that you'd be especially loyal to a party if it's not the norm of your social milliu. Do you know how the two groups within the party broke down in primaries?