Once you adopt a pattern and a mold of conduct with all of the laws involved, including your Constitution, and it's been in being for over a hundred years, people don't change their habits.
As a result, the elite minority of the Democratic Party was left without competition to rule the South virtually unchallenged for the next several decades. The reign of the Democratic one-party system from roughly 1910-1950 is commonly referred to as the “Solid South.” An example of their influence is seen in election results of the period. For instance, with only two exceptions (1920 and 1928), southern states cast all their electoral votes for Democratic presidential candidates from 1880 to 1944. Also, between 1919 and 1948 Democrats won 131 of 132 senatorial seats and 113 of 114 gubernatorial elections throughout the South. Such party loyalty ensured southern political leaders enormous power in Congress, where southern Democratic senators and congressional delegates consistently controlled both the Senate and the House. Southerners regularly became chairpersons of powerful committees, so that by the 1950s the South commanded about 60 percent of congressional chairs in spite of its relatively small population (Encyclopedia of Southern Culture 1169).
The lack of inter-party competition caused low participation rates in state and regional elections. What remained of the public’s political interest shifted to the process of presidential primaries. The primaries were a series of caucuses and elections to decide each party’s presidential nominee. Initially, the Democratic primaries of southern states were white primaries – open only to the white electorate. Since the Solid South was essentially a one-party system, exclusion from the Democratic primaries meant a de facto exclusion from the presidential election process altogether.
In the 1920s, the American Civil Liberties Union (ACLU) began challenging the white primaries. Their success was limited until the Texas case of Smith vs. Allwright was taken all the way to the Supreme Court. Ultimately, in 1944 the Texas white primary was ruled unconstitutional. While the Smith vs. Allwright decision was specific to the Texas primary, the ruling led many states to voluntarily end their white primaries.