San Jose, Calif. ? As if California officials don’t have enough to worry about ahead of the bewildering gubernatorial recall vote Oct. 7, computer scientists say shoddy balloting software could bungle the results and expose the election to fraud.

Some computer experts are worried that shoddy software could affect results of the Oct. 7 recall election in California. Arnold Schwarzenegger, above, is one of 135 candidates bidding to replace Gov. Gray Davis.

Their worst-case scenario is the accidental deletion or malicious falsification of ballots from the 1.42 million Californians who could vote on electronic touch-screen machines. These voters comprise 9.3 percent of the state’s 15.3 million registered voters.

The software experts also warn that if any candidate contests the election, a meaningful recount would prove impossible because four counties — including two of the largest — don’t provide paper backups to the electronic machines. The other counties still use punch-card machines, optical scanners or other systems that provide physical evidence of votes.

“We should put in the safeguards as soon as possible — especially in an election that’s going to be so complicated and difficult,” said David Dill, a computer science professor at Stanford University.

The campaign to get printers and paper receipts included with electronic voting machines gained momentum in July, when a team from Johns Hopkins and Rice universities issued a report criticizing the 33,000 electronic machines already in use nationally that are made by Diebold Election Systems.

Diebold, based in North Canton, Ohio, produced a 27-page rebuttal, accusing researchers of a “multitude of false conclusions.” Dozens of elections officials have vouched for the security of Diebold systems since the July 23 report.

Given the prevalence of computerized systems, the criticism is irresponsible, said Mischelle Townsend, registrar of voters in Riverside County, which has 4,250 touch-screens for 650,000 voters.

“The scientists are undermining people’s confidence in democracy,” Townsend said. “None of the critics is giving any credence to the extensive system of checks and balances that we employ internally.”

But some advocates of electronic voting, including the Leadership Conference on Civil Rights, are backing off their praise in the study’s wake.