Your assumption and Rove’s is that Carson had four votes per precinct to lose. Also the assumption is that each of those votes, if they existed would go to Cruz alone. Since Carson’s numbers actually outperformed his expected numbers it is possible the efforts of Cruz’ people, presuming that made the effort, were a failure. And do we really need a POTUS who makes Al Gore’s reaction to Florida 2000 seem positively majestic.
No secret Rove has it out for Cruz for being too conservative.