In the case of Munro v. Socialist Workers Party, 1986, the U.S. Supreme Court ruled in favor of Washington state's "blanket primary" system that required a political party to receive at least one percent of votes in a primary election for its candidates to appear on the general election ballot. The Socialist Workers Party argued this law violated their First and Fourteenth Amendment rights by limiting their access to the electoral process and restricting voters' choices. However, the court held that these minor burdens on constitutional rights were outweighed by Washington’s interests in ensuring that parties had a modicum of support before gaining ballot access, avoiding voter confusion caused by overcrowded ballots and protecting against frivolous candidacies. Therefore, it was concluded that such restrictions did not violate any constitutional protections.

In the dissenting opinion for Munro v. Socialist Workers Party, Justice Thurgood Marshall argued that Washington State's requirement of a minor party to receive at least one percent of votes in the primary election to appear on the general ballot was unconstitutional. He believed it violated First and Fourteenth Amendment rights by imposing an undue burden on minor parties' political expression and association. Marshall pointed out that this rule could potentially exclude a candidate who might have had significant support in the general election but failed to meet the arbitrary one percent threshold during primaries due to low voter turnout or strategic voting practices. Furthermore, he emphasized that states must show compelling interest when enacting laws limiting constitutional rights - something Washington failed to do convincingly according his interpretation.