Hart would have cracked more of the south than that, both times.
Against Reagan, no way
Against Bush, it's possible, but Bush actually did better than Reagan in many Southern counties.
Um, no. Reagan, especially, wasn't a great deal more popular in the south compared to the rest of the nation. Look at 1980 county map.
But Bush actually did better in many Southern counties than Reagan, and even did better in the entire state of Tennessee. It was very surprising to me.
For example, compare the 1984 and 1988 Georgia maps:
1984:
1988: