In Smith v. Allwright, the U.S. Supreme Court ruled that denying African Americans the right to vote in primary elections was a violation of the 15th Amendment. The case originated from Texas where Lonnie E. Smith, an African American man, was denied a ballot for a Democratic Party primary election due to his race by S.S Allwright, an election official. At this time in Southern states like Texas, winning the Democratic primary essentially guaranteed victory in the general election because of one-party rule; thus excluding black voters from primaries effectively disenfranchised them completely. The court's decision overturned its previous ruling on Grovey v Townsend (1935) which had upheld "white primaries". This landmark case marked significant progress towards voting rights and racial equality as it ended white-only participation within political parties' candidate selection processes.

In the dissenting opinion for Smith v. Allwright, Justice Roberts argued that the majority's decision to invalidate Texas' white primary elections was an overreach of federal power into state affairs. He contended that political parties were private entities and thus had a right to determine their own membership rules without government interference. Furthermore, he asserted that there was no constitutional violation because African Americans still had the opportunity to vote in general elections; they were only excluded from participating in one party's primaries. Therefore, according to Justice Roberts, this case did not involve racial discrimination but rather a question of states' rights and individual liberties which should be respected by the Supreme Court.