Voter fraud true story: my local director of elections sent me a letter saying that there was a discrepancy between the signatures on my ballot and my voter registration ... but *I hadn't sent my ballot in yet*. I live in Canada right now and vote electronically in general elections, but my paper ballot still gets mailed to my dad's house in Oregon. Pop tossed my ballot into the recycling bin, knowing I vote online, but someone stole my ballot out of the bin and tried to vote as me.
I contacted the county elections manager and let them know the situation, and they've discarded the other ballot, so everything's worked out. But there's a good lesson here for those of you in vote-by-mail states: DESTROY unused ballots!