How did southern democrats try to reverse the political gains of African Americans?

The southern Democrats legislated Jim Crow laws, which segregated black people from the white

population

Explanation:

During the Reconstruction period of 1865-1877, federal law provided civil rights protection in the U. S. South for freedmen, the African Americans who had formerly been slaves.

So In the 1870s, Democrats gradually returned to power in the Southern states, sometimes as a result of elections in which paramilitary groups intimidated opponents, attacking blacks or preventing them from voting.

Gubernatorial elections were close and disputed in Louisiana for years, with extreme violence being unleashed during the campaigns.

In 1877, a national compromise to gain Southern support in the presidential election resulted in the last of the federal troops being withdrawn from the South.

White Democrats had regained political power in every Southern state. These conservative, white, Democratic Redeemer governments legislated Jim Crow laws, which segregated black people from the white population, and upheld them constitutionally as "separate but equal" rights.

Still, most Southerners, black and white, remained trapped in an "Old South" of poverty. Losing Ground in Education During Reconstruction.