Crypto-Gram: April 15, 2004:
"Stealing an Election

There are major efforts by computer security professionals to convince government officials that paper audit trails are essential in any computerized voting machine. They have conducted actual examination of software, engaged in letter writing campaigns, testified before government bodies, and collectively, have maintained visibility and public awareness of the issue.
The track record of the computerized voting machines used to date has been abysmal; stories of errors are legion. Here's another way to look at the issue: what are the economics of trying to steal an election?… "

http://www.schneier.com/crypto-gram-0404.html#4