No third candidate is receiving any press, so it would have to be extremely close for the winner not to break 50%.
Democrats are going to vote for Thad today. The Cochran campaign has been pushing this. And the Palin and Santorum endorsements are motivating the militant democrats to do just that. It is hilarious to see democrats get so unhinged that they want to go vote for an old man who they have always opposed.