Rationalthought: To be clear, I don't think the monitoring is unusual, it is the leaking. It is likely that US intelligence agencies find evidence of US political scheming and some level of wrongdoing on a regular basis, but ignore it because that sort of thing is far outside their mandate. (Famously, J Edgar Hoover had dirt on a large array of politicians.)

Certainly in this case the wrongdoing itself should be the primary focus, not the person or persons who leaked it, since in the case of Flynn at least it was clearly in the public interest. But the context of where this information is coming from is something to watch.