However I don't think most administrations would attempt to achieve them by disrupting the press corps. That claim probably can't be tested or evaluated fairly, partially because it's a fairly novel action, and partially because it's a complex hypothetical. I must admit it is just my political leanings driving me to this conclusion.

I guess another (unfair) way to look at is: I would rather have someone appear not to attempt to manipulate public opinion, regardless of if they actually are, because when you are at that level of power, I at least want you to ave your act together enough to keep halfway-decent PR. Thus the fact that it appears to me that they are making such weak attempts to manipulate says something, independent of the ethics of the action itself.

Trump goes beyond preferences... he only wants favorable questions from organizations that will cover him favorably.