How did the passage of the Voting Rights Act of 1965 impact political participation?

Since the civil war voting for African Americans had been repressed by the southern states. They had literacy tests, poll taxes, and questions on the constitution. The civil rights voting act made these things illegal and put the discriminatory Jim Crow laws on notice that the federal government would take action. In recent years some of the voting rights act has been tested and watered down and in a reversal states have been passing laws restricting voting in certain areas or districts to discriminate against people living in these areas. Instead of moving forward for civil rights it seems that there is a movement to go back 40 years.