Voting is one of the main ways racial resentment expresses itself politically. The two are deeply intertwined. You can't cleanly separate one from the other.
And your framing is ahistorical. You're collapsing several very different political eras into one and misrepresenting how power actually shifted. Republicans were already winning national elections well before the late 1970s, and the Democratic "dominance" of the mid-20th century depended heavily on a racially exclusionary Southern bloc.
The major realignment wasn't driven primarily by economic downturns but by civil rights and the restructuring of racial and regional politics. Economic stress mattered, but it didn't create the shift, it helped mobilize it.
The New Deal is a perfect example of this, because the coalition explicitly excluded Black Americans to maintain white Southern support.