A "Ren Giovanni" just put this comment on a (very) old blog post:
Our absentee ballots had our party affiliation written on the mailing envelope. Isn't this an invitation to electoral fraud?What's to keep some mailhandler from the opposite party from chucking our ballots?
Short answer: yes.
Read this article by Edmund Newton to find out all about it. I believe we can file this under in the "weird and wrong things done by the Broward County Supervisor of Elections Office" folder.