Scattered technical problems were reported in the early hours as voters in 10 states, including California, New York and Ohio, went to the Super Tuesday polls to choose a Democratic presidential nominee and decide primary contests for congressional and state races.
Advocates of electronic voting say paperless ballots save money and eliminate problems common to old systems. But the technology brings a new breed of security concerns, like software errors and hackers that could make the results unreliable.
In California, new security measures range from random tests of touch-screen machines by independent computer experts to a recommendation that poll workers prevent voters from carrying cell phones or other wireless devices into booths.
Overall, some 10 million people in at least two dozen states were expected to cast ballots in primaries this year on machines built by Diebold, Sequoia Voting Systems, Electronic Systems & Software and other vendors.
And the electronic voting trend is accelerating: In November's presidential election, at least 50 million people will vote on touch-screens, compared with 55 million using paper, punch cards or lever machines, according to Washington-based Election Data Services.
One Maryland polling place had to switch to paper ballots Tuesday because its new electronic voting machines didn't work. State elections supervisor Linda Lamone said technicians expected to have the problem fixed quickly.
Voters also had to start out using paper ballots in Georgia's Effingham County. Chris Riggall, a spokesman for Secretary of State Cathy Cox, said county officials apparently forgot to program the encoders — devices used to tell ballot access cards, which voters insert into the machines, what ballot to display.
A security issue also arose in Georgia.
Georgia Tech student Peter Sahlstrom said he found 10 Diebold terminals sitting unprotected in the lobby of the school's student center Monday. Sahlstrom, 22, photographed the machines in their unlocked cases.
"Frankly, this makes me nervous and ... it validates a lot of the concerns I already had," Sahlstrom said in a phone interview.
The paperless ballots eliminate problems like hanging chads and make it impossible to accidentally vote twice for one position. The machines also can toggle between different languages for people who don't speak English.
"The modernization of the nation's voting infrastructure is long overdue," said Alfie Charles, spokesman for Oakland-based Sequoia, which built the machines being used by as many as 4 million voters in California and Maryland.
But computer scientists have been protesting the switch. They're particularly concerned that few of the computers provide paper records, making it nearly impossible to have meaningful recounts, or to prove that vote tampering hasn't occurred.
Politicians, voter-rights advocates and even some secretaries of state have acknowledged that the systems could theoretically fail — with catastrophic consequences.
In several software and hardware tests, critics have shown it's easy to jam microchip-embedded smart cards into machines, or alter and delete some votes — in some cases simply by ripping out wires. They've cracked passwords to gain access to computer servers and showed that some systems relying on Microsoft Windows lacked up-to-date security patches that should have been downloaded from the Internet.
California Secretary of State Kevin Shelley directed elections officials last month to bolster security in 12 counties using touch-screens. Those counties account for about 41 percent of California's registered voters. Shelley also wants independent, random tests of touch-screen machines.
Maryland, which spent $55.6 million on 16,000 touch-screen computers earlier this year, also took precautions.
Computer experts told Maryland lawmakers in January that the hardware contained "vulnerabilities that could be exploited by malicious individuals." Among their surprises: all of Maryland's machines had two identical locks, which could be opened by any one of 32,000 keys or be easily picked.