Goldwater was more of a black belt white and low country white candidate. Regions and areas in the poorer, less diverse and more pro-New Deal areas tended to not respond as favorably in cases where he won them (hence NE MS mentioned above) or even outright vote against him as happened in places like Tennessee.
Wallace on the other hand skewed far more in the opposite direction while Nixon became the default candidate of the low country and growing Southern suburbs. Look at South Carolina
1964 and
1968 Note the impact of the rise of black voting and its impact in the black belt in flipping most of those counties to the national Democratic ticket, leaving Republicans to the cities and suburbs and remaining white majority low country counties.