I am surprised this has not come out yet, but the Rio Grande border counties in Texas are actually a pretty good response.
In particular, Starr County, TX is now the new recordholder for longest Democratic streak (not Republican since 1892). And unlike in the cases of say, majority black Southern counties, in this case the Dem base has not changed.
And same applies for most of the general area. Even in R landslides this area voted titanium D with the same kind of people voting D.
I mean, the point of this thread is areas that vote the same party bur for different reasons, so this answer, while correct, it's a bit "swing and a miss".