The South strongly supports Republicans in federal elections not necessary state elections. The animosity of the old South was directed at the federal government not the state government. As a consequence the South votes for Republican Presidential candidate over 75% of the time. Southern Republicans out number Southern Democrats in the House. In the Senate, Southern Republicans out number their Democrat counterparts 2 to 1.The following states have Democrat majorities in both houses their state legislatures:
Alabama
Arkansas
Louisiana
Mississippi
North Carolina
States with split houses split houses:
Kentucky
These states have Republican majorities in both houses:
Florida
Georgia
South Carolina
Tennessee
Source
Tell me again how the south is solidly Republican?