In this significant decision, the US Supreme Court established jurisdiction for federal courts in cases on reapportionment of state legislatures, repealing its 1946 ruling that only elected officials could determine apportionment.

Baker addressed the clear disparity in the number of voters within Tennessee's legislative districts. Voters in lesser populated rural districts had more political power; those in larger urban districts thus incurred vote dilution and a denial of equal protection. The Court apportioned the size of Tennessee electorates for all elective offices by establishing the principle of “one person, one vote.” Its decision also enlarged the doorway to black voter representation in southern legislatures.