Elaine Ginnold, registrar of voters for Alameda County, said the rejection rate there hovers around 10 percent, a total that would be expected with any new system. However, she also noted that the new system could kick out eligible voters.

County election officials said the new registration system requires that potential voters provide a driver's license number or other identifying information to a county registrar. The data is keyed into a local database and periodically uploaded to the new centralized system, which matches it with information from the California Department of Motor Vehicles and other agencies to verify that it's authentic.

The rigorous system will reject applications whose data doesn't exactly match the confirming documents. Even small discrepancies, such as a missing middle initial, could cause an application to be rejected.

"My main concern is there could be 20,000 to 30,000 new registration cards delivered to Alameda County at the registration deadline," Ginnold said. The deadline for the state election is May 22.

The registration information takes a week to process into the Alameda database before it is sent to the state database for matching, which can take up to five days, Ginnold said. "We would get the kick-outs only a few days before the election -- which won't allow enough time to manually validate them," she said.