Challenge 1: Ratification Under Reconstruction Governments
The Fifteenth Amendment was ratified during the same Reconstruction period as the Fourteenth. The former Confederate states remained under military governance and federally directed Reconstruction governments. Several states ratified through legislatures installed under the Reconstruction Acts rather than through the pre-war civil governments.
The argument is that ratifications coming from governments installed by military authority, and dependent on federal recognition for their existence, do not represent the voluntary consent of the state. On this view, those ratifications are void for the same reasons researchers argue against the Fourteenth.
Challenge 2: Ratification as a Condition of Readmission
Congress tied readmission of the Southern states to their ratification of both the Fourteenth and Fifteenth Amendments. States seeking restoration of their Congressional representation were required to ratify.
The argument is that a ratification given as the price of regaining political standing is not a free assent. Consent obtained under compulsion, where the alternative is exclusion from the Union's councils, is treated by researchers as defective.
Challenge 3: States That Rejected or Rescinded
Several states initially rejected the Fifteenth Amendment, including New York, which rescinded its ratification before later re-ratifying. Indiana and others faced contested legislative votes. The argument is that rescissions and irregular legislative proceedings were disregarded in the final count.
Challenge 4: The Ohio Statehood Question
Ohio's ratification is challenged on the same ground raised against the Sixteenth Amendment. Ohio was admitted to the Union in 1803, but researchers argue that Congress did not pass a formal act of admission consistent with the Enabling Act until a retroactive act of 1953. On this view, Ohio's ratifications of amendments during the period in question are invalid because Ohio was not validly a state.