California already was among 26 states requiring electronic voting machines to produce a backup paper record for voters to see and confirm their electronic votes.
If the governor signs the bill, the state will join a dozen of those states where elections officials also plan to use those printouts for any automatic recount or an election challenge. California is close on the heels of New York, West Virginia and other states that passed similar laws within the last two months, according to researchers at Electionline.org, a nonpartisan clearinghouse for voting-reform information.
State senators sent the bill to the governor on a lopsided 36-0 vote after scarcely any debate.
Computer scientists conceived of the paper trail as a partial safeguard against fraud and error in computerized voting.
"No voting machine is going to be 100 percent error-free, 100 percent of the time," said Debra Bowen, D-Marina Del Rey, the bill's author. "But unlike with paper, when it comes to electronic data, a small human error, a technology glitch or a tampering incident can change thousands of votes in an instant."
Her legislation would treat electronic ballots as the legal record of the vote, but rely on the paper trail for California's mandatory hand-count of ballots in 1 percent of precincts.
"People need and deserve to know their votes have been counted accurately, and the best way to ensure that is to make sure there's a paper printout of every electronic ballot," she said.
So far, the paper trails produced by computerized touch-screen voting machine suppliers have been double-rolls of curly, thermal paper that tend to jam on some machines.
"Boy, it's pretty clunky. And it didn't have to be this clunky," said David Wagner, an assistant professor of computer science and a voting-security scholar at the University of California, Berkeley. "The vendors could have built machines with a paper trail that was more convenient for elections officials and voters, but it didn't happen."
Local elections officials who embraced electronic voting as a way to rid themselves of paper fought the paper trail and fought its use in recounts.
California's chief elections officer, Secretary of State Bruce McPherson, has opposed Bowen's bill because he says the paper rolls don't look anything like a ballot and shouldn't be treated like one.
But if Gov. Arnold Schwarzenegger signs the bill aides said he has made no decision voters in counties using touch-screens could be seeing paper trails for a long time, and those little slips could become ensconced in state election law as a decider of elections.
That's because no one has come up with a better idea for confirming an electronic vote in detail. Two voting companies have devised machines that would issue a coded slip of paper to every voter. In a clever bit of cryptology, voters then could check by phone or the Internet to see whether a ballot corresponding to that code was counted.
But voters still would not know whether their vote counted as they intended.
"I don't see anything on the near horizon and so my guess is for the next five to 10 years paper will be the preferred alternative," said Berkeley's Wagner. "We're a long ways from having paperless electronic voting that's secure."
If a new technology for verifying votes did come along, experts on voting and elections say they doubt elections officials will have the money or desire to buy it for several years at least.
"You just see counties wanting to slide through this and get it done," said Sean Greene, Electionline.org's research director.
After the 2006 elections, he and Wagner said, voting technology is likely to settle down.
"Elections officials are not going to have the appetite to change their systems for some time," Wagner said.