“The Commission was established by the Civil Rights Act of 1957 as an independent, bipartisan fact-finding federal agency, empowered to “investigate allegations in writing under oath or affirmation that certain citizens of the United States are being deprived of their right to vote … ‘ Since its inception, the Commission has frequently examined the state of voting rights. Congress mandates the Commission to issue one annual statutory enforcement report; the Commission, by majority vote, selected this topic to be its 2018 report.”