Final answer:
African Americans in the South during Reconstruction primarily joined the Republican Party, the party of Lincoln, who had fought for their freedom and rights. The Republican support for black suffrage was partly to establish a political base in the South, but African American support for the party lasted well into the 20th century, even as Republicans started to aim for a broader white electoral base.
Step-by-step explanation:
During Reconstruction, African Americans in the U.S. South overwhelmingly joined the Republican Party. This affiliation arose because it was the Republicans, the party of Abraham Lincoln, who fought for the rights of freed slaves and worked to integrate African Americans into society. Reconstruction brought a significant transformation of Southern politics, shifting from an all-white, pro-slavery, Democratic stronghold to Republican-led states that included African Americans in positions of power for the first time in American history.
Although the Democratic Party regained control of the South after the end of Reconstruction post-1877, the trust and political relationships established between African Americans and the Republican Party during Reconstruction persisted. Black suffrage was a key aspect Republican leaders advocated for, primarily to protect the rights of African Americans and to establish a political base in the South. However, this initial support did not translate into long-term prioritization of African Americans' needs as the Republicans began accommodating the racism of Southern whites to broaden their electoral base among white voters. Despite this, African Americans had few alternatives to supporting the Republicans as long as Democrats remained the party of white supremacy. This pattern started to shift as new Democratic leaders began to court black voters in future decades.