Smith vs Allwright
Smith v. Allwright , 321 U.S. 649 (1944), was a landmark decision of the United States Supreme Court with regard to voting rights and, by extension, racial desegregation. It overturned the Texas state law that authorized the Democratic Party to set its internal rules, including the use of white primaries. The court ruled that the state had allowed discrimination to be practiced by delegating its authority to the Democratic Party. This affected all other states where the party used the rule.
The Democrats had excluded minority voter participation by this means, another device for legal disfranchisement of blacks across the South beginning in the late 19th century.