"There was a failure rate of about 10 percent, and that's not good enough for the voters of California and not good enough for me," Secretary of State Bruce McPherson said.

If the machines had been used in an election, the result could have been frustration for poll workers and long lines for thousands of voters, elections officials and voter advocates said Thursday.

"We certainly can't take any kind of risk like that with this kind of device on California voters," McPherson said.

Rejection of the TSx by California, the nation's largest voting-system market, could influence local elections officials from Utah, Mississippi and Ohio, home of Diebold corporate headquarters, where dozens of counties are poised to purchase the latest Diebold touch screens.State elections officials in Ohio say they still have confidence in the machines.

But McPherson's decision did send California counties from San Diego to Alameda to Humboldt hunting for potential alternatives to their plans to use the TSx.

By January 2006, every polling place nationwide must offer at least one handicapped-accessible voting machine ? touch screens are one example ? and all California touch screens must offer a countable paper record so voters and election officials can verify the accuracy of electronic votes. So far, no voting system has been state approved that meets both requirements.

"This is a muddle because there is no certified system right now," said Elaine Ginnold, acting registrar of voters in Alameda County. "We have to look at all of the nonoptions."

McPherson denied approval of the TSx after a series of failed tests, culminating in a massive, mock election conducted on 96 of the machines in a San Joaquin County warehouse. San Joaquin is one of three California counties that purchased a total of 13,000 TSx machines in 2003 for more than $40 million and have paid to warehouse them ever since.

For eight hours July 20, four dozen local elections officials and contractors stood at tables and tapped votes into the machines to replicate a California primary, one of the most complex elections in the nation. State officials watched as paper jams cropped up 10 times, and several machines froze up, requiring a full reboot for voting to continue.

Diebold Election Systems Inc. plans to fix the problems and reapply for California's approval within 30 days, company spokesman David Bear said.

"They had 10,000 ballots and 10 paper jams. Obviously that needs to be looked at and addressed, and it will be," he said. "But it needs to be put into perspective."

Elections officials and voting activists said they had never heard of more extensive testing for a single voting system, outside of an actual election. Kim Alexander, president of the Davis-based California Voter Foundation, said McPherson deserves credit for ordering rigorous testing.

"It's the first ever conducted in the state and, to my knowledge, in the country that simulated a real-world experience with these machines in a voting booth," she said.

Ordinarily, states and the National Association of State Elections Directors approve voting systems after labs hired by the manufacturers perform tests on a handful of machines. The Diebold TSx managed to get through those tests ? twice. But none of the testing standards addresses printers on electronic voting machines, even though more than 20 states either require a so-called paper trail or are debating such a requirement.

For years, voters have reported frozen screens and other glitches in the polling place.

"It's always been the voters' word against election officials' and the vendors'," Alexander said. "Now we have real proof right before the eyes of state elections officials."

Reliable voting equipment has been a problem before for Diebold in California. In the weeks before the March 2004 presidential primary, the firm rushed a new device called a voter-card encoder through assembly, testing and temporary state approval. Hundreds of the devices broke down on election day. Without the devices, thousands of voters in two of California's largest counties, San Diego and Alameda, could not vote on Diebold's touch screens. Lines developed, and hundreds walked away without voting.

California withdrew approval for some Diebold voting systems, and company stock sagged. Elections experts said McPherson's decision probably saved the company from a repeat.

"Diebold for some is sort of teetering on the public-relations edge, and so something like this, with 10 percent of the voters potentially affected, that would be a pretty big PR issue for Diebold," said Sean Greene, research director for Electionline.org, a nonpartisan voting-reform clearinghouse.

In the Bay Area, Alameda and San Joaquin counties had planned to use all TSx machines in the 2006 elections, and Marin County planned to put at least one machine in each of its polling places.