Which amendment to the U.S. Constitution protects citizens from voter discrimination based on race?

The 15th Amendment is the correct choice because it explicitly prohibits the federal and state governments from denying a citizen the right to vote based on "race, color, or previous condition of servitude." Ratified in 1870, this amendment was a significant achievement following the Civil War and aimed to secure voting rights for African American men, although it took further legislative and societal efforts to ensure these rights were fully realized.

In the context of voter discrimination, while the 12th Amendment addresses the electoral process for the president and vice president, and the 19th Amendment guarantees women the right to vote regardless of sex, neither addresses racial discrimination. The 24th Amendment, ratified in 1964, prohibits poll taxes in federal elections but does not directly address racial discrimination. Thus, the 15th Amendment remains the foundational constitutional protection against racial voter discrimination.