Insights From Other Strategists - Thurgood Marshall On The White Primary System

Thurgood Marhshall was, of course, a Justice of the Supreme Court. But before that, he was an absolutely incredible litigator; he was the primary strategist behind the NAACP's litigation campaign to desegregate public institutions. In the wake of his victory in Brown v. Board of Education, he published The Rise & Collapse of the "White Democratic Primary," 26 J. Negro Educ. 249 (1957). 

The "white primary system" was a system of rules and tacit agreements in Jim Crow South that effectively disenfranchised African-Americans. At the time, the Democratic Party held a virtual monopoly on public office in the region. The party was not explicitly regulated by the Constitution, and so could make its own rules, including prohibiting certain class of people (like African-Americans) from voting. If you couldn't vote in a Democratic primary, you were essentially excluded from the real election.