SEATTLE – A U.S. District Court judge today struck down Washington state's new "top two" primary system, approved by voters last fall, as unconstitutional, saying it infringed on the rights of political parties to pick their own nominees for office.

In a 40-page ruling, Judge Thomas Zilly said the state cannot allow voters to skip back and forth along party lines as they pick a favorite candidate for each office. Nor can it allow candidates to identify themselves by party without that party's approval, the ruling said.

The state Republican, Democratic and Libertarian parties sued in May to challenge Initiative 872, which created a primary system in which the top two vote-getters for each office advanced to the general election, regardless of political affiliation.