Smith v. Allwright

Smith v. Allwright (1944), was a landmark decision by the United States Supreme Court. The decision made it unconstitutional to keep African Americans from voting in a Democratic Party primary in Texas. By extension it covered white primaries in all states. It overturned "Grovey v. Townsend" (1935) which had allowed the Democratic party to hold all-white primaries that excluded black voters.
The all-white primary.
The Reconstruction Amendments to the United States Constitution gave African Americans freedom from slavery, citizenship and the right to vote. But many former slave states came up with ways to keep blacks from voting. These included poll taxes, literacy tests and complex voter registration laws. While these worked in most southern states, it did not work in Texas. The party needed the Hispanic vote but wanted to exclude blacks. They needed also to split the black and hispanic vote. Texas, like most southern states, was a one-party state. The Democratic party controlled politics. The state and local primary elections decided which candidate would ultimately win office in the general election. Democrats in Texas used the "white primary" to serve their purposes. It prohibited non-whites from joining the Democratic party and taking part in primary elections. It could be used also to exclude Mexican Americans in areas of the state where the party did not need them. The Reconstruction Amendments applied to the state. But in "Grovey v. Townsend" the state of Texas was allowed to pass on its responsibility for protecting black voter rights to a private organization—the Democratic party. This allowed Texas to use the all-white primary.
The case.
In another decision, "Grovey v. Townsend" (1935), the Supreme Court decided that the Democratic Party was a private organization. Their state convention could decide who can be a member. Lonnie E. Smith, a Houston dentist, and the National Association for the Advancement of Colored People (NAACP) decided to fight this decision. 
In Smith v. Allwright (1944), the court overturned the Grovey ruling. A majority of the justices decided that the Democratic party was more than a private organization. It was a part of the election process in Texas. For this reason the court said that it was unconstitutional to stop African Americans from voting in the Democratic primary.