With the U.S elections just days away, some voters in states including West Virginia, Texas and Tennessee have reported that electronic touch-screen voting machines are 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. (For more about e-voting technology, see our page.)

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 (formerly Diebold) in Allen, 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.