I know a way to prevent fake opposition slates in the future: use weird-colored paper. Either distribute at the last minute or actually print at the last minute. The opposition can get on their laptops and copy your title, your formatting, everything... but they will not have neon green paper (or whatever) because they will not have thought to bring colored paper, and even if they did they cannot have a supply of every conceivable possible color. And it will be too late for them to run to Office Depot and buy some. Then if there are two "Conservative Unity" tickets, a real one and a Romney one, you just tell everyone to vote for the neon green ticket.