There were then, and still are, a handful of “white ethnic” pockets left in the Bronx — Throgs Neck, Morris Park (Italians), and Woodlawn (Irish) — so probably voters from there. Also perhaps to a lesser extent some rich people in Riverdale.
The Italian community there is one of the most culturally conservative in NYC.
Can you provide a specific source. (I don't doubt you; I just would be interested to read about this if possible b/c I'm not from NYC and haven't been there enough to understand this anecdotally).
I'm from Long Island and I worked in NYC in my younger days. I've been to NYC hundreds of times, all 5 boroughs. The Morris Park neighborhood is one that I knew people from there in college. The entirety of Throgs Neck and Morris Park is about half Hispanic now, but the Italian neighborhoods in Morris Park remain cohesive and conservative.
