Most southern blacks were denied their right to vote. The biggest obstacle was the poll tax, a special tax that was required of all voters but was too costly for many blacks and for poor whites as well. Voters also had to pass a literacy test to prove that they could read, write, and understand the U. S. Constitution. These tests were often rigged to disqualify even highly educated blacks. Those who overcame the obstacles and insisted on registering as voters faced threats, harassment, and even physical violence. As a result, African Americans in the South could not express their grievances in the voting booth, which for the most part, was closed to them. a. There were many obstacles that stopped African Americans from being able to vote. b. Tests stopped African Americans from voting. c. Those who overcame the obstacles and insisted on registering as voters faced threats, harassment. d. The biggest obstacle was the poll tax.