It can include control over your image, how you are perceived by people and how well you are received by people. To a greater extent, it covers relationships with friends and more importantly, enemies and how you can appeal to their self-interest. By failing to control his expressions, his emotions, McCain gave us a handle to exploit, a sense of who he is that was detrimental to his campaign.

It can include how you can take advantage of current events. For example, who do many/most people blame for the financial crisis and how can you leverage that information to craft your own message. How can you tap into what people are feeling, how can you tap into general bias to direct a message.

It can include the tools you use to gather information and how well you understand that information in crafting a message. How effective are those tools, how are those tools perceived in terms of credibility, etc.

It can include the tools you use to directly influence opinion, and that includes the people you employ, your surrogates. A lot of people are describing Rahm Emmanuel (for example) as...let's just say "abrasive". Maybe that's fine, so long as the man can use those traits effectively to influence people.

It can even include your ability to define/redefine terminology. Take, for instance, words like "liberal", "mandate" or "bipartisan". I think it's obvious that the Republicans have been very effective here, taking ownership and getting people (ie. the media) to use those words in the way Republicans want. If you can, by simply describing something as "liberal", tap into negative, preconceived notions about what that particular word means, you can more easily establish a sort of control over people, not by appealing to their intellect but by exploiting their unconscious feelings and attitudes.

It might be better to describe the environment as being a collection of variables. How many of those variables can you change or influence? What is out of your control, and can you neutralize it or turn it to your advantage?

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Most political goals are need driven.  Very rarely do you anything that could truly be called a new initiative, in the sense that the idea and plan arose from within the administration.

Americans must be cultivated to first see a need, then the opportunity cost of failure to address the need.  

No President can truly control his environment, as it were.  The experiences and expectations of the population are too diffuse.  Sure, there are commonalities, like desire for a common defense.  But then you have to answer more questions: How?  How big will the military be?  Who get to serve?  Do gays?  Do we continue to rely on preemption as a philosophy?  Do we need more infrastucture?  Questions such as those drive the political equation; the administration must decide in most cases according to the greatest good for the most.  Thus, passage of any bill depends upon a cogent reading of the prevailing opinions throughout the country.

If it means manipulating the public's perception about the environment (which I think Steve M discussed upthread), then the Republicans tried that but reality, as they say, bites.

The Overton Window, from wikipedia:  

It describes a "window" in the range of public reactions to ideas in public discourse, in a spectrum of all possible options on an issue. Overton described a method for moving that window, thereby including previously excluded ideas, while excluding previously acceptable ideas. The technique relies on people promoting ideas even less acceptable than the previous "outer fringe" ideas. That makes those old fringe ideas look less extreme, and thereby acceptable. Delivering rhetoric to define the window provides a plan of action to make more acceptable to the public some ideas by priming them with other ideas allowed to remain unacceptable, but which make the real target ideas seem more acceptable by comparison.

The degrees of acceptance of public ideas can be described roughly as:

    * Unthinkable
    * Radical
    * Acceptable
    * Sensible
    * Popular
    * Policy

The Overton Window is a means of visualizing which ideas define that range of acceptance by where they fall in it, and adding new ideas that can push the old ideas towards acceptance merely by making the limits more extreme.

This is what the Republicans have excelled at. They pour millions into think tanks, media outlets, lobbying, and outreach efforts to promote their ideas. It doesn't matter that they might be extreme in most peoples eyes - it creates a powerful infrastructure of support for those ideas because they have succeeded in making them mainstream. Simple as that. Republicans badly dominate this game - just read this article from The American Prospect: http://prospect.org/cs/articles?article=the_mighty_wurlitzer  This is why on our side, the blogosophere is important, and supporting our think tanks like Economic Policy Institute, Center for American Progress, Children's Defense Fund, etc are so important. In terms of controlling your environment, thats where the battle takes place. The politicians are playing a different type of game that is framed by that larger battle.