“Although it is common to think of Jim Crow as an explicitly race-based system, in fact a number of the key policies were officially colorblind. As previously noted, poll taxes, literacy tests, and felon disenfranchisement laws were all formally race-neutral practices that were employed in order to avoid the prohibition on race discrimination in voting contained in the Fifteenth Amendment. The laws operated to create an all-white electorate because they excluded African Americans from the franchise but were not generally applied to whites.”