Most people know, intuitively or explicitly, the difference between rationality and rationalizing: The first implies a careful consideration of as many likely possibilities as one can manage, and determining the best option for overall success and well-being. The second has to do more with justifying a pre-determined course of action, or (more simply put) giving reasons to do what we really want to do. There are a number of well-written posts on these two themes over at Less Wrong, so I won't add much more on the distinction between these two.
What I will note, however, is an observation regarding the presuppositions that are at work in our cultural conscientiousness (at least as I perceive it). By and large, we work with the assumption that the majority of people, especially people in power, are more or less rational. Sure, we recognize the ideologically-driven component of partisan politics (see, for example, the impasse on spending and debt at the national and state levels). When it comes to making decisions (even within a particular ideology), we assume that most people function day-to-day as rational beings. What's more, we take for granted that those whose job it is to think rationally and clearly—academics or judges, for example—actually do so.
Sooner or later, though, we're going to have to come to grips with this false assumption, this vestigial remainder of Enlightenment principles.
Barack Obama, while a careful thinker in the eyes of many, almost certainly still engages in rampant rationalization. This is because he, like every other being on the planet, possesses a brain that isn't set up to process the world with fidelity to evidence, at least not with anything approaching the ideal of humans as "a thinking animal."
Our brains are evolutionary "turduckens," in that our evolutionary ancestors slowly added structures to the brain, and only rarely removing structures, until we arrived at homo sapiens. (Though, of course, the evolution of the brain has not ceased.) And, since our relatively high capacity for rational thinking and exploration are rather new additions to the structure of our brain, we need to recognize that, in fact, we still possess strong non-rational tendencies in our thought. Things we may not even be aware of—for example, what we ate for breakfast—can influence the way we think (see here). More importantly, concerns like self-preservation, food insecurity, flight-or-fight, etc., continue to make their presence felt in a society rather free of life-threatening situations.
We can only minimize the degree to which physiological, emotional, and sub- or unconscious motivations cloud our ability to think critically, clearly, and rationally. Ignoring the reality that none of us, not even presidents and professors, can always think rationally is only to convince ourselves of a lie—that is, to rationalize what we want to be the case.