Twitter user SpeedMcCool did some research not only into the 1972 U.S. Senate results, but also into the district boundaries of the Representative Districts back in 1972. Bravo SpeedMcCool.
You notice that the state’s politics have reversed. Back in 1972, the Newark, Dover and Wilmington suburbs were Republican while New Castle, inner city Wilmington and all the rural areas in New Castle, Kent and Sussex counties were Democratic.
Since there’s no chance that downstate DE was especially progressive, all of those rural voters probably explain some of the more retrograde (retrograde IMO) aspects of Biden’s early politics.
Dixiecrats in Sussex .
Newark suburbs to the north were Republican, but those to the south and east were Democratic even then.
Basically, the northern rim was Republican except for Claymont, and remnants of that didn’t disappear until the past few years.
And, as Russell Kirk Melrath indicates above, rural racists were still loyal Democrats in 1971.