One interesting thing is that one of his best cities appears to have been Tampa which surprises me as to my knowledge Tampa does not have a particularly high Jewish population. Yet he crossed 9% in Hillsborough County.
The Internet (and Google) is amazing. I googled: "Why did Henry Wallace do so well in Tampa in 1948?" and came up with this:
https://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=1373&context=sunlandtribuneThe Latin community was quite prominent in the Tampa areas of Ybor City and West Tampa in 1948. Wallace won seven precincts in those areas that year. A tiny bastion of radicalism in an otherwise conservative region.