Not always, but this one was. When Clinton signed the bill that ended Glass-Steagall (which turned out to be a horrible idea), he did it as part of a quid pro quo with Gingrich. Not a good decision, but deals are how things happen in Washington. That is not what happened here. Pressuring a foreign government to investigate your top political rival by withholding promised aid - the specifics are what makes it an abuse of power, not the overall concept of "you scratch my back, I'll scratch yours." That said, there are plenty of actions that on the surface aren't necessarily crimes, but reach the point of illegality because of the specifics. Dershowitz's comment is like saying "engaging in sexual conduct with another person alone is not a basis for a felony." Sure, but there are plenty of times when it is.