If Newt doesn’t win SC this thing is over.
Not necessarily. Newt can be a close second to Mitt and the race will continue so long as Santorum is way behind Newt. Romney only has momentum if he is up above 30% and Newt and Santorum are fairly even. If Newt pulls away from Santorum then Newt becomes the leading non-Romney candidate, and if there is one non-Romney and 70% of voters are choosing someone other than Romney then Newt still has a path forward to the nomination. Santorum needs to either match or beat Newt in SC (and FL if he's still in) or get out.