On Monday, the U.S. Supreme Court stuck down that system, ruling that states violate political parties' rights when they allow primary election voters to cast their ballot for any candidate, regardless of affiliation.
CBS News Correspondent Bob Fuss reports the California system was approved by Golden State voters in a referendum and was used for the first time in March of this year, allowing any voter to vote for any candidate for any office, regardless of party. In their 7-to-2 decision, the justices ruled the blanket primary system robbed political parties of any control over who their candidates are and threw it out.
But the high court's decision was a narrow one and it did not outlaw the more common "open primaries" used in another 20 states. Open primaries let voters choose on primary day whether to vote in the Democratic or Republican contest.
"This is clearly a victory for political parties, which don't like or trust these crossover primary votes, and it is clearly a defeat for California, which passed the blanket primary law," said CBS News Legal Consultant Andrew Cohen.
"Depending upon the precise language used by the justices," Cohen added, "the decision is likely to cast a shadow on primaries in other states - like Alaska, Washington and Louisiana - which allow some form of crossover voting. I think we may see the effects of this decision soon and for many years to come."
Among the friend-of-the-court advice the justices received in the California case was a pro-blanket primary brief from Sen. John McCain, the Arizona Republican who relied heavily on Democrats and independents in his failed bid for the GOP presidential nomination earlier this year.
McCain got strong boosts from victories in New Hampshire and Michigan - states with open primaries - but in California, he finished third behind Democrat Al Gore and Republican George W. Bush.
Writing for the court, Justice Antonin Scalia said California was "forcing political parties to associate with those who do not share their beliefs. And it has done this at the crucial juncture at which party members traditionally find their collective voice and select their spokesman."
"The burden (California's voting system) places on (the political parties') rights of political association is both severe and unnecessary," Scalia wrote.
Scalia said states could hold a nonpartisan blanket primary, in which voters can choose any candidate regardless of affiliation, and the top two vote-getters move on to the general election. The system he described would be similar to Louisiana's system.
Under such a voting plan, Scalia said, "primary voters are not choosing a party's nominee" and therefore political parties' rights of free association are not harmed.
His opinion was joined by Chief Justice William Rehnqist and Justices Sandra Day O'Connor, Anthony Kennedy, David Souter, Clarence Thomas and Stephen Breyer. Dissenting were Justices John Paul Stevens and Ruth Bader Ginsburg.
Four California political parties - the Democrats, the Republicans, the Libertarians, and the Peace and Freedom Party - challenged the blanket primary system. The system's supporters argued the blanket primary encouraged voter turnout and lead to the nomination of more moderate candidates. But the four parties said allowing nonparty members to vote would harm their members' ability to choose candidates that best represent their views.
A federal judge ruled against the parties and the 9th U.S. Circuit Court of Appeals agreed, saying the state had a substantial interest in boosting voter turnout and giving voters a greater choice.
In appealing to the nation's highest court, the parties' lawyers said the California system was an assault on their ability to choose nominees who represent their ideology.
"As for affording voters greater choice, it is obvious that the net effect of this scheme ... is to reduce the scope of choice, by assuring a range of candidates who are all more centrist," Scalia said.
Stevens, writing in dissent for himself and Ginsburg, said the court should "respect the policy choice made by the state's voters" in approving the proposition.
Washington state's blanket primary system dates back to 1935, and Alaska has used a similar system for most years since 1947. In Louisiana's blanket primary system, the top two vote-getters, regardless of party, go on to a runoff election.