Just a suggestion... While you are in the midst of making you laymen legal case here, one place to start your research might be on the topic of limitations and exceptions to copyright laws.
However, it might save you some time to just skip it and realize that these campaigns are run by professional staff that include actual lawyers. I suspect any copyright issues were vetted before this ad was produced.
I didn’t “make a laymen [sic] legal case here,” I simply said:
Does Cruz even have the legal right to use these clips without Limbaugh’s permission - or has Limbaugh GIVEN him permission?
That’s called a “question.” Clearly you don’t know the answer. Anyone else? Has Rush commented on this? I would think he would frown on the use of audio clips from his show being used in a political ad, since he’s made it a point that he’s not going to endorse anyone during the primaries.