[codedokode]

Tampering with voting machines software is easier, less noticeable and doesn't even require a cooperation from staff at the polling station (which ballot stuffing requires). You just need cooperation from the manufacturer.

[XorNot]

And of note, the manufacturers of voting machines get out there and make public statements that they are not politically neutral - https://www.nytimes.com/2003/11/09/business/machine-politics...