Having the exact people independents (and we) don't like effusively singing his praises could easily have been machivellian to hurt him or at least make him dependent on their support as their opponents scattered.... once voters ignored 'establishment' gop in Delaware and Alaska and became dangerous the GOP might have only wanted to 'support' tea party candidates in name. However, I also think they like the idea of Rand winning BIG and spurring on voters to the west. They may have decided he is going to win, but their ads aren't helping to push him win 'big' so they'll move on.
Or it could be exactly what they say it is. I'm just speculating.
But I still say it points to the fact that some here who thought and were telling others that 'Rand has it in the bag we can focus elsewhere, and let the outside groups take if from here' were premature at best.