Voters of San Diego County, prepare to darken ovals again. This time, please remember to fill out the entire oval.

Late Friday evening, Secretary of State Debra Bowen ended months of suspense by declaring several electronic voting systems not secure enough for use in California. Bowen had good reason for her very expensive decision, which comes after counties have spent several years and millions of dollars in upgrading their voting equipment. But it has thrown the state's election system into turmoil just months before a major election cycle begins.

At best, Bowen's forced march back to paper ballots promises to restore integrity to our democracy. At worst, the secretary of state has just squandered millions of our tax dollars. We'll hope for the former while fearing the latter.

Twenty of the state's 58 counties use the electronic voting systems that Bowen decertified on Friday. San Diego's supervisors paid $31 million for 10,200 touch-screen machines from Diebold Systems in late 2003. Now, the only voters who will vote on the Diebold machines are those who vote early at the registrar of voters office or those who are physically challenged. Even then, Bowen ordered counties to enforce a suite of strict security measures.

No one argues that the machines in question are impervious to corruption. Any computer system can be hacked. Bowen's eight-week "top-to-bottom" review, during which special teams of computer experts were given not only unlimited access to the machines but computer coding and manuals as well, only confirms what we already knew.

It also bears repeating that these machines are not networked. To influence elections on any significant scale, a large, organized group of tech-savvy intruders would have to hack into a large number of machines individually. That's not an impossible scenario, but it's not very likely either.

Still, the investigation uncovered several disturbing vulnerabilities. It found that common office tools can be used to open the machines and delete votes or inject preprogrammed "smart cards" that cast multiple ballots. Even these machines' paper receipts, which are supposed to guard against fraud, can be manipulated as well.

Most unsettling of all, UC Berkeley researcher David Wagner determined that hackers can install viruses that spread throughout a voting network when ballots are tabulated by a central computer. Unless these serious flaws are addressed, electronic voting will never gain the trust of enough voters to sustain our democracy.

That said, the paper ballots to which we are returning have their own set of problems.

While testing the touch-screen ballots, investigators showed that opti-scan machines used to count paper ballots can also be easily infiltrated, as they use the same flawed election-management software as the touch-screens. These problems are serious enough that, in an overlooked part of her Friday decision, Bowen ordered the opti-scan machines decertified and then recertified them with strict new security protocols.

Even if they're counted properly, paper ballots can still cause problems. Locally, the city of San Diego's November 2004 mayoral election went to incumbent Dick Murphy because 5,547 voters failed to fill in the ovals next to Donna Frye's name.

Bowen's bold decision will either restore confidence in our voting system or lay the groundwork for expensive electoral chaos next year. We may have entered a disturbing era in which too many voters have too little trust in the mechanisms of our democracy. Should paper ballots prove just as susceptible to tampering as electronic voting, we may have to stop seeking the perfect voting system, but instead settle for the best one we can afford.