SACRAMENTO, Calif. - In another blow to the political status quo, Californians will vote next Tuesday on a ballot initiative that would scrap the primary system for state and congressional elections. Instead, voters could cast ballots for any candidate regardless of party affiliation, with the top two vote-getters advancing to the general election.

The result could be two candidates from the same party or two well-funded candidates.

Proponents of Proposition 14, such as Republican Gov. Arnold Schwarzenegger and Lt. Gov. Abel Maldonado, argue that the change would benefit moderates who often stumble in primaries where party activists have an oversize say in the outcome.

"When there's an open primary, a top two, you better have three qualities: Be open-minded, be reasonable, and be pragmatic, because now you have to connect with all the voters," said Maldonado, a former Republican lawmaker and rancher.

Understandably, the political parties oppose the idea, fearing a loss in clout. That has created an odd alliance in which Republicans and Democrats have joined to try to defeat the measure. The parties argue that if their organizations are marginalized, special interests will fill the void.

"Political parties are important for three key reasons - they are broad-based, democratically governed, and transparent," said Ron Nehring, chairman of the state Republican Party. "You cannot say the same of special-interest groups."

An anti-incumbent, anti-Washington sentiment has prevailed this election year, with several tea party-backed candidates knocking off those tapped by the political establishment. The California ballot initiative reflects the frustration with partisanship and the political system.

So far, voters who appear hungry for political reform agree with proponents. A poll released May 19 by the Public Policy Institute of California found 60 percent of likely voters supported Proposition 14, with 27 percent opposed.

Party leaders acknowledge that an open primary will reduce their influence. They uniformly oppose the measure, creating an unusual alliance against it.

Members of the Green and the Peace and Freedom Parties have begun running television ads opposing Proposition 14. Their candidates are likely to be shut out of general elections if the measure passes.

U.S. House Speaker Nancy Pelosi (D., Calif.) also has come out against the measure. Rep. Zoe Lofgren, who heads California's Democratic congressional delegation, said that while the idea might look good in theory, "in the real world it will only lead to less choice and more entrenchment."

Supporters say the initiative will boost moderate candidates, but open elections haven't always given centrist politicians a ticket to the finals.

In 1991, Louisiana voters sent former Ku Klux Klan leader David Duke to a runoff in the governor's race. Duke's organization and funds helped him edge out the more moderate candidates in an open field, said Rob Richie, executive director of FairVote, an arm of the nonprofit Center for Voting and Democracy.

California voters have a mixed record on open primaries. In 1996, they adopted Proposition 198, which allowed all voters to cast ballots for any candidate. It advanced the top vote-getter from each party in the primary to the general election. It was struck down four years later by the U.S. Supreme Court for violating the First Amendment right of free association. In 2004, voters rejected an open-primary measure similar to Proposition 14.

"People register as a member of a political party for a reason," California Democratic chairman John Burton said. "It allows people to at least have an idea of what your values are."