The upcoming presidential election is expected to be a close one, and election watchdog groups like Verified Voting and Common Cause have expressed concerns about paperless voting machines. Direct Recording Electronic systems (DREs), which record votes using touchscreens or push buttons, will be used in 16 states. Many DREs don't provide a paper trail that can be used to audit the election, as reported in a recent Computer World article.

"You can't do a post-election vote tabulation audit in such cases because there is no independent record of the votes," said Pamela Smith, president of Verified Voting. "You are checking the system against itself. It is sort of a circular argument," she said. Even a few incorrect or missed votes could change the outcome in a tight election, particularly in a swing state.

Several states, including Texas, Colorado, Florida, Virginia and Pennsylvania, use a combination of paper ballots and DRE systems, viewed by watchdog groups as superior to an electronic-only system.

Others laud the benefits of paperless voting machines, pointing out that humans make errors too, whether or not paper is involved. However, in 2004 a touchscreen DRE in Carteret County, N. C., lost 4,500 votes following a memory problem. Because there were no paper records, it was impossible to know how those votes should have been counted. The state has since moved to a combination of paper ballots and digital systems.