In tight elections, the loser often calls for a recount. But recounting ballots might not be easy in states that use paperless machines — including the presidential battleground state of Pennsylvania.

Why would anyone allow for a voting machine that has no paper trail? Without a paper trail, anyone with access to the computers tallying the votes could change the results and there would be absolutely no proof of the tampering.

Could this be the reason why in recent years after switching to electronic voting machines with no paper trail, exit polls stopped being accurate?

Who knows? We’ll never know until we put back in a system that can be properly audited. And a paper trail has always been the best system, far better than no auditing system at all.

Source: Why Worries About Paperless Voting Loom Larger This Year : NPR