The Supreme Court has upheld the state of Washington's open primary election system. By a 7-2 vote, the court says the state may use a primary system that allows the top two vote-getters to advance to the general election, even if they are from the same party. Washington never held a primary under the new system because of legal challenges. Writing for the majority, Justice Clarence Thomas said that overturning Washington's plan would have been an "extraordinary and precipitous nullification of the will of the people."

The top-two plan was created after state voters approved a law in 2004 allowing them to pick their favorite candidate for each office. The top two vote-getters would advance to the November general election, even if they are from the same party. The major parties challenged the law in federal court, asserting a First Amendment right to select their own nominees without outside interference.