The potential problems have provided fodder for McPherson's critics, who claim that he selected rigid guidelines that could unfairly penalize voters.

The voter database has "been a disaster for anyone who is trying to register for the first time or reregister because they moved, got married and need to change their name or change parties," said California State Sen. Debra Bowen, who held a hearing this week on the matter. A spokesman for Bowen said the rejection rate should be between 1 percent and 2 percent.

The U.S. Department of Justice, which enforces HAVA, worked with McPherson's office as the system was being crafted.

The secretary of state's office has set up processes to offer guidance to counties and voters on fulfilling the new requirements, McPherson's spokeswoman said. He has also proposed legislation to "provide common-sense flexibility so that no eligible voter should be denied the opportunity to vote because of a technicality," she said.

Ginnold said that ultimately, a centralized database that has a single entry for each voter can successfully prevent fraud. Previously, election officials relied on local databases and registration rules, and exact matches weren't required.