Discussion on answer by Barmar: Can Trump legally investigate Bruce Springsteen?

@Barmar Right. And police officers can often effectively murder people and plant weapons on them to cover it up, but the presumption here is always that people are asking about what is legal and illegal, not about what is effectively possible or feasible. I don't expect anyone to address anything in particular in their answers, but I can say that one probably cannot fully answer the question without reference to campaign-finance laws and the First Amendment.