From Ed Felton, one of the Princeton researchers who demonstrated the vulnerability of the Diebold voting machines, we learn they are even more vulnerable.

On Wednesday we did a live demo for our Princeton Computer Science colleagues of the vote-stealing software described in our paper and video. Afterward, Chris Tengi, a technical staff member, asked to look at the key that came with the voting machine. He noticed an alphanumeric code printed on the key, and remarked that he had a key at home with the same code on it. The next day he brought in his key and sure enough it opened the voting machine.
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It’s a standard part, and like most standard parts it’s easily purchased on the Internet. We bought several keys from an office furniture key shop — they open the voting machine too. We ordered another key on eBay from a jukebox supply shop. The keys can be purchased from many online merchants.