Volkswagen stock plummeted today, because of accusations by the Environmental Protection Agency that VW uses software that turns on its emission control device when the software detects that one of its diesel cars is undergoing emission testing. When not being tested, the software disables the device, thereby causing the car to spew as much as 40 times the pollution limit of the Clean Air Act.
Like VW cars, modern voting machines contain software that is tested before use in elections. It would not be difficult to write voting machine software that would, like the VW software, know when it is being tested, and thus behave correctly during testing but not during an actual election. If such behavior were detected after an election, the vendor stock would plummet, but so would voter confidence in the outcome of the election. Furthermore, in the case of some voting systems that cannot be legitimately recounted, such as paperless voting machines or online votes, there would be no way to determine after the election if the declared winners were the actual winners.