Just because you call it that doesn’t make it true. Was it necessary for them (CNN or Cruz) to run with the story, probably not but that doesn’t mean it’s dirt politics. What do you think the motive of CNN was? What is the motive for Trump to bash anyone who he chooses? The obvious answer is to make the others look bad. For CNN it is to show support for Hillary, for Trump it is to get votes.
No media outlet said that Carson was dropping out. That was an assumption Team Cruz unilaterally made and later had to apologized for.
Not rocket science.