Which factor most contributed to the split among southern Democrats in 1948?

A. the Supreme Court's decision in Brown v. Board of Education

B. Senator Joseph McCarthy's investigation of the State Department

C. Earl Long's campaign for the Democratic presidential nomination

D. President Truman's support for desegregation and civil rights

The correct answer is D. The factor that most contributed to the split among southern Democrats in 1948 was President Truman's support for desegregation and civil rights. They were called Dixiecrats.

Explanation:

Dixiecrats were a conservative faction in the Democratic Party from 1948 to 1964, that supported racial segregation and the Jim Crow laws.

In 1948, it was composed by 6 governors, 19 senators and 1 member of the House of Representatives from the southern states, which at that time were the stronghold of the Democratic Party and racism. The leader was Strom Termond. The group broke away from the Democratic Party, dissatisfied with Truman's attempts to desegregate in the South. In 1948, the dixiecrats voted in the presidential election for Strom Thurmond under the slogan "Segregation Forever." After the defeat in the elections, the Dixiecrats returned to the Democratic Party, but continued to maintain their faction, actively resisting desegregation, after which they were joined by Robert Bird and Albert Gore Sr. (father of A. Gore). A racist bloc was formed of 21 Democratic senators and right-wing Republicans. After the elimination of segregation in the South and the beginning of the "new southern strategy" of the Republicans led by Barry Goldwater, Richard Nixon and Ronald Reagan in 1964, most of the Dixiecrats led by Strom Termond joined the Republican Party.