Final answer:
The tactic used to prevent African Americans from voting by mandating a small fee was the poll tax.
Step-by-step explanation:
The tactic used to prevent African Americans from voting by mandating a small fee is the poll tax. A poll tax was a fee imposed on individuals to exercise their right to vote. This tactic, often accompanied by other discriminatory practices, was used to suppress African American voter turnout during the Jim Crow era in the United States.
Learn more about Voting rights suppression