If you really cannot bring yourself to vote for one of the candidates tomorrow, declining your ballot is a possibility. It certainly beats staying at home and not bothering to vote.
If you really think you're going to send anyone a message by declining your vote, you're not protesting, you're letting people like me who will be voting make the choice for you.
Simply put, how many declined ballots were there in the last election? Did anyone post the numbers anywhere? Did the papers and the TV news say "Oh my, there were declined ballots!"?
As a protest, declining your ballot is about as useful as yelling at a tomato in your kitchen. No one really cares except for the tomato and it ain't telling anyone.
Think about it, and think hard, after you decline your ballot there's no going back until the next election and you'll get to live with whatever the rest of your community decides.
Vote tomorrow, it's your right.