One of five measures before voters, Proposition 14, which was approved Tuesday, will scrap the political primary system in favor of an open contest in which only the top two vote-getters would advance to the general election, regardless of party affiliation.
It is one of three propositions that would amend the state Constitution.
Other ballot measures ask Californians to experiment with public funding of political campaigns, impose voter oversight of public power and authorize insurance companies to charge higher rates to drivers who have not always carried car insurance.
The open primaries measure has pitted the state's political parties against Gov. Arnold Schwarzenegger, who has long argued that centrist candidates rarely win primaries dominated by party activists. Schwarzenegger's campaign committee donated $2 million to support the effort while the California Chamber of Commerce has given $720,000.
The campaign's public face has been Lt. Gov. Abel Maldonado, a Republican who as a state senator last year leveraged his budget vote and agreed to raise $13 billion in taxes if lawmakers agreed to put Proposition 14 on the ballot.
The other election-related measure, Proposition 15, would open the door to public funding of political campaigns in California after a 26-year ban. Voters rejected the prop with 57 percent of the vote.
Despite California's largest utility pouring the most money into Proposition 16, voters rejected the measure. Pacific Gas & Electric Co. contributed $46 million to Prop 16 in a ploy to stymie competing public power agencies from expanding into new territory and to discourage municipalities from starting their own utilities.
Another business-backed initiative, Proposition 17, put on the ballot by Mercury Insurance in a bid to overturn a state law that prohibits insurance companies from considering a driver's insurance history to set rates, was rejected with 52 percent of the vote. The measure would have allowed loyalty discounts to follow costumers if they switch insurance companies.
The third largest auto insurer in the state, Mercury has contributed nearly $15 million to fund the campaign.
Voters overwhelmingly adopted Proposition 13, a measure that would exempt earthquake-safety improvements from property taxes. The proposition put on the ballot by the Legislature would prevent counties from raising property taxes on buildings retrofitted to withstand earthquakes until ownership changes.
Current law exempts owners of unreinforced masonry structures, such as those made of brick or cement blocks, from higher property taxes for 15 years after they make seismic improvements.