Raising the broader issue of felony disenfranchisement is right on: it was actually in the course of researching that issue that I discovered Peter Wagner’s work in the Prison Policy Initiative (see my link on the phrase “for about a year and half”).

Here is some interesting historical background, to compliment the Virginia example, mentioned by Spencer Overton, at the link you provided.

Mississippi’s 1890 constitutional convention was among the first to use felon disenfranchisement laws against African Americans. Until then, Mississippi law disenfranchised those guilty of any crime. In 1890, however, the law was narrowed to exclude only those convicted of certain offenses – crimes of which African Americans were more often convicted than whites. The Mississippi Supreme Court in 1896 enumerated these crimes, confirming that the new constitution targeted those “convicted of bribery, burglary, theft, arson, obtaining money or goods under false pretenses, perjury, forgery, embezzlement or bigamy.”

Other states followed suit. Many newly disenfranchisable offenses, such as bigamy and vagrancy, were common among African Americans simply because of the dislocations of slavery and Reconstruction. Indeed, the laws were carefully designed by white men who understood how to apply criminal law in a discriminatory way: the Alabama judge who wrote that state’s new disenfranchisement language had decades of experience in a predominantly African-American district, and estimated that certain misdemeanor charges could be used to disqualify two-thirds of black voters.

“What is it we want to do?” asked John B. Knox, president of the Alabama convention of 1901. “Why, it is within the limits imposed by the Federal Constitution, to establish white supremacy in this State.”

The laws worked. A historian later hired by Alabama state registrars found that by January 1903, the revised constitution “had disfranchised approximately ten times as many blacks as whites,” many for non-prison offenses.

(Alec Ewald, “Punishing at the Polls: The Case Against Disenfranchising Citizens With Felony Convictions,” emphasis added.)

As seems to frequently be the case, Mississippi set the example for everyone else on how to maintain segregation and discrimination. As is also the case, these innovations were not limited to the South. Ewald also notes that New York state adopted felony disenfranchisement laws in 1821 in order to exclude Blacks from the political process.