What does “Somebody is too much in one’s head” mean in contrast to “Somebody is in over one’s head”?

There was the article titled “Thunder Road” in New York Times’ (January 11) that began with the following sentence

“I have learned two things covering politics. One, first impressions are often right. John Edwards is slick. Hillary Clinton is expedient. W. was in over his head. Barack Obama is too much in his head. Chris Christie can be a bully.”

http://www.nytimes.com/2014/01/12/opinion/sunday/dowd-thunder-road.html?hp&rref=opinion

What does “Someone is too much in his head” imply in contrast to “Somebody is in over one’s head”? Does it mean he is smart, but lacks the power to fulfill his promises and plans?

We call a person who is intelectual but lacks action and power to execute “Atamadekkachi -頭でっかち – man with a too big head’ in Japanese. Is someone ‘being too much in his head’ equivalent to “Atamadekkachi"?

I think it amounts to meaning "too cerebral"—that is, too prone to considering multiple interpretations of data and the various pros and cons of possible reactions to them, without getting from that stage to the concrete response. Another way to express this criticism would be "too much thought, not enough action." It can also mean not giving due consideration to what other people are thinking or how they are likely to act—a problematic quality in a politician or strategist.

In contrast, "in over one's head" means "in a role or position that one is not competent (either by native ability or training) to perform satisfactorily."

“Someone is too much in his head” means that the person is over thinking things and probably should accept the simple answer/solution. The US military has an acronym K.I.S.S. which stands for "keep it simple stupid" as in don't make things more difficult than they need to be.

The previous answer for "in over one's head" is already well stated as; "in a role or position that one is not competent (either by native ability or training) to perform satisfactorily."