At the heart of the Nunes memo controversy is the hard nugget of fact that the target of the FISA approval for surveillance was directed at a man named Carter Page. The FBI got such approval once and renewed it three more times. They convinced a FISA judge that Page, a U.S. citizen, was likely a black hat, working for a foreign government.
I can find no evidence that anybody has ever filed an indictment against Carter Page for being an agent of a foreign government. Can you? Makes you wonder how many more innocent souls are being carefully watched, and for what nefarious purposes.
On the other hand, if watching an apparently innocent Page was merely a means to surveilling the Trump campaign, because as a suspected agent of a foreign power all his contacts could also be surveilled, the whole thing comes into focus. It can be seen as a sham done for political purposes.
Maybe I overstate the case; the problem is nobody wants to make the case with evidence that there was every reason to suspect Page and his associates even though it turned out he was okay. Now it looks like a political hit job and we are being asked to trust people who appear to have acted in an untrustworthy manner. That dog won’t hunt.