Are some touch-screen voting machines really "flipping" votes from one candidate to another, or are the voters who claim their votes are being changed just wrong?

With the US elections just days away, some voters in states including West Virginia, Texas and Tennessee have reported that electronic touch-screen voting machines are "flipping" their votes to another candidate on the screen.

When those allegations are made, e-voting hardware vendors and local election officials usually blame errant fingers, overhanging jewelry or clothing -- or they argue that the touch-screens weren't properly calibrated. But continuing reports about flipping -- sporadic though they may be -- raise questions about the machines themselves, when they were designed and what kind of usability testing was done.

Computerworld asked the four major e-voting machine vendors to talk about how their hardware was originally designed, with an emphasis on whether real-world user testing was done as the devices were being drawn up.

Vendors defend their designs and say they have been proven through sales figures in the marketplace; e-voting critics note the vote-flipping accounts by voters and worry that the machines could cast doubt on the legitimacy of elections.

Chris Riggall, a spokesman for Premier Election Solutions (formerly Diebold) in Texas, said that vote-flipping reports are taken seriously. "It's one of those things that when a voter says this occurs, well, I wasn't there, you weren't there, but we can't say that they didn't have that experience," he said. "The key is that poll workers immediately need to be asked for assistance if that happens" so the ballot can be corrected or cancelled if needed.

A touch-screen machine can be checked for proper calibration to make sure the spot on the screen that's touched registers the proper vote on the electronic ballot -- or a voter can be redirected to another machine in the polling place, Riggall said.

Despite a smattering of reports elsewhere, there have been no complaints of vote flipping in Georgia, where almost a million people have already cast early ballots using Premier touch-screen machines. "There has not been one claimed occurrence of what is really a calibration issue in all of those votes that have already been cast here," he said. "The nature of a touch-screen device [is that], like any other device, there can be an instance where it's not operating properly. What the majority of our jurisdictions find is that where 'vote flipping'..or mis-selection is occurring .., in the vast majority of cases they find that the calibration is not out of specification."

Instead, he said, a voter's "fingernails can definitely have an impact, the length of a fingernail." If a voter has long nails, "there's no question that you can touch the adjoining choice" and make the machine appear to change a selected vote. "There may be instances where that is occurring."