Final answer:
The southern Democrats who left the party to maintain segregation were called the Dixiecrats. They emerged in reaction to the Democratic Party's support for civil rights and became a precursor to the southern shift towards the Republican Party during the Regan Revolution.
Step-by-step explanation:
Southern Democrats who left the Democratic Party because they wanted to retain segregation were known as the Dixiecrats. This term specifically refers to members of the States' Rights Democratic Party, which was formed in 1948 as a breakaway faction of the Democratic Party in reaction to its increasingly pro-civil rights platform. The Dixiecrats strove to uphold the segregationist social order of the South and were staunch proponents of states' rights, which they believed were being eroded by the federal government's efforts to impose racial integration. The splintering of the Democratic Party and the Dixiecrats' alignment with conservative ideologies paved the way for many white Southern voters to eventually shift their loyalties to the Republican Party by the 1980s, especially during the Regan Revolution, which solidified conservative control over the South.