Ok, let's take an example. The ballot looks like this:
_Obama (Democrats candidate)
_GW Bush (Republicans candidate)
_Lefty Wingbat
_Right Nutcase
_Greeny McGreenpants
_Glorious Faggot
_Fascist Bullyboy
_Darkie Killer
_Mohammed Mohammed
If you're going to vote for more than one person, you're going to vote for your personal cause, and then for one of the top two mainstream choices.
So, it all but guarantees that whoever leads the media leads the polls, and whoever leads the polls will be chosen along with whatever minor issue candidate you pick.