Answer :
In general, it is true that the southern Democrats "dumped Truman from the Democratic ticket in the 1948 election" but this was not a set-in-stone conclusion.
Harry S. Truman became President of the United States in 1945 and remained in office until 1953. Among his many achievements, Truman managed to establish several policies that marked a difference not just in the U.S, but also the world, after the effects of World War II. One of these policies became known as the famous Marshall Plan, which was an economic intervention that sought to help western Europe after the war and another one was the Truman Doctrine. However, one of the home fronts in which Truman became very much involved, was the furthering of the civil rights movement through a series of executive orders that, among many other things, prohibited segregation, overturned poll taxes and forbid lynching. These reforms, took place between 1947 and 1952, and probably one of the best known was the establishment of the President´s Committee on Civil Rights, in 1947, among many others. The results of these policies set by the Truman administration caused fury in the Democratic Party and a good faction of the Southern Democrats decided to split away from the party and form a new one called State´s Rights Democratic Party, or, Dixiecrats. Correct answer here then is A: they formed a new party and ran their own candidate for president in 1948. This candidate was South Carolina´s Governor Strom Thurmond.