Up until the post-World War II period, the party’s hold on the region was so entrenched that Southern politicians usually couldn’t get elected unless they were Democrats. But when President Harry S. Truman, a Democratic Southerner, introduced a pro-civil rights platform at the party’s 1948 convention, a faction walked out.
These defectors, known as the “Dixiecrats,” held a separate convention in Birmingham, Alabama. There, they nominated South Carolina Governor Strom Thurmond, a staunch opposer of civil rights, to run for president on their “States’ Rights” ticket. Although Thurmond lost the election to Truman, he still won over a million popular votes.
It “was the first time since before the Civil War that the South was not solidly Democratic,” Goldfield says. “And that began the erosion of the southern influence in the Democratic party.”
After that, the majority of the South still continued to vote Democratic because it thought of the Republican party as the party of Abraham Lincoln and Reconstruction. The big break didn’t come until President Johnson, another Southern Democrat, signed the Civil Rights Act in 1964 and the Voting Rights Act in 1965.