Project Management is politics. Whether done well or poorly, the art and science of the possible is the key practice of the person (Project Manager) who leads a complex, multiparty innovation.
Seeing the job this way provides the appropriate lens for the great majority of people I work with every year, but the general philosophy of our culture equips us all poorly to focus the lens correctly.
For one thing, in this polarized age you're a weenie if you don't batter any opposing party with supercharged overreactions to meaningless differences. For another, we prefer tidy quantifications to accurate qualifications -- meaning we are conditioned to reduce complexity to two-dimensional formulas without regard to how accurate or useful it is to do so.
As a result of those and other underlying cultural norms, we tend to have trouble with managing to results in complicated, nuanced situations. A key complication is that participants invariably begin with differing -- sometimes opposing -- intentions.
Dealing constructively with ambiguity. That's effective management. Since Project Management is management boiled down to a thick (sometimes harsh) brew, both the constructiveness and the ambiguity tend to be harder to handle.
I'm fresh from a visit to the "Guide to the Project Management Body of Knowledge," the PMBOK Guide of the Project Management Institute. The Guide does not claim to be a Bible for the profession; it presents itself as a compendium of specific points of knowledge that a competent Project Manager should possess. The actual use of the knowledge is up to the individual, and that competency is earned through practice, study and training.
The PMBOK Guide is therefore rich in quick references to the essential working skills of the people manager, but light in the how-tos of those skills. The words "negotiate" and even "politics" show up often enough, but you get to Page 409 in the Fourth Edition before you find three pages of summary of eight skill components of what I call the politics of Project Management.
(PMI does provide extensive listings of books and other materials that thoroughly cover the landscape, including the people-leadership skills I prize so highly. One of my favorites is V.K. Verma's "Human Resource Skills for the Project Manager," published by PMI itself.)
This is not a criticism of the Guide. It is just a word of caution to aspiring Project Managers: Knowledge is not power. Skill is. And the skill of managing diverse insterests to mutually satisfying outcomes (i.e., politics) is the ultimate, most satisfying, skill of all.