As for the Dems' argument that it's a campaign slogan, the sign could just say something like: "The ballots were printed before the resignation of Republican candidate Mark Foley. He has been replaced as the Republican candidate by Joe Negron." That is NOT a slogan, just a clarification.
But if you vote for the dead Democrat his wife gets his Senate seat?
They'd look at your sign the same way they look at the 10 Commandments. They'd be afraid someone might actually read it!