* Ambiguous wording and subjective application: Literacy tests weren't standardized. Administrators could arbitrarily decide what constituted "literacy," allowing them to fail Black voters who might have been literate while passing white voters who were not. The tests themselves were often complex and obscure, even for educated individuals.
* Lack of educational opportunities for Black people: Following slavery and Reconstruction, Black people in the South faced systemic denial of education. They lacked access to schools and resources, making it far more difficult for them to pass literacy tests designed to be challenging. This disparity created a readily exploitable inequality.
* Enforcement and intimidation: The tests were not administered fairly. Black voters faced intimidation and harassment at the polls, making the process even more difficult and discouraging participation. White election officials were often overtly biased, actively working to prevent Black votes.
* Legal framework: While the 15th Amendment prohibited denying the right to vote based on race, color, or previous condition of servitude, the vagueness allowed loopholes. Literacy tests were presented as race-neutral, even though their effect was overwhelmingly discriminatory. Legal challenges were difficult to win due to the complexity of proving intentional discrimination.
* Complicity and inaction: While there was some opposition, broader societal acceptance of white supremacy and the desire to maintain the existing power structures fueled the success of these discriminatory practices. Federal intervention to meaningfully counteract this disenfranchisement was weak or non-existent for decades.
In short, the success of literacy tests wasn't just about the tests themselves but a systemic strategy combining unequal access to education, prejudiced administration, intimidation, and the exploitation of legal loopholes to effectively suppress the Black vote. They were a key tool in establishing Jim Crow laws and maintaining racial hierarchy in the South.