All we need from Newt is just enough of a performance to somehow get Mississippi and Alabama in the Romney column. If that happens, it would be the nail in the coffin. It would be nice. I do not think it is going to happen, but it looks more likely after seeing Tennessee/Oklahoma, and factoring in Newt's momentum boost from Georgia. There is a 10-20% probability whereas earlier tonight I would have put it at 5%.
I wouldn't bet on it. In Tennessee and Oklahoma, Mitt got less than a third of the three-man vote. Alabama and Mississippi are unlikely to be any better for him. So if Rick and Newt split the vote exactly, all Mitt will get out of it is an embarrassing third.