Cruz has a massive ground game in SC, and his superpac has paid a bunch of people to canvass for him as well.
With that said two things need to be taken into consideration:1) Cruz does not have the same level of endorsements he had had in Iowa... Jeb, and Rubio have him beat there. 2) This is an open primary not a caucus. If Trump keeps it up he’s going have a lot of dems and indys come onto his side.
It worked in Iowa that was it