An ExpressVote XL voting machine demonstration in Philadelphia. Advocates say paper ballots are good, but not sufficient, in a new era of security challenges.

An ExpressVote XL voting machine demonstration in Philadelphia. Advocates say paper ballots are good, but not sufficient, in a new era of security challenges.

An ExpressVote XL voting machine demonstration in Philadelphia. Advocates say paper ballots are good, but not sufficient, in a new era of security challenges.

An ExpressVote XL voting machine demonstration in Philadelphia. Advocates say paper ballots are good, but not sufficient, in a new era of security challenges.