One way to look at that is to treat US elected offices, especially the executive as a form of hierophany - which in sociology of religion denotes an object that by the virtue of its physical form embodies the qualities of the sacred.
The US booboisie has generally little understanding of the so-called policy issues - they do not understand how economy and society work, they have no clue about countries other than the US, and they even have difficulties finding them on a map. Thus, they have no reason to chose this or that candidate - or for that matter to care for the whole process at all. As a result, half or more of the US population does not even bother to vote, which ironically is the most rational choice, given the circumstances (i.e. their state of knowledge).
Many of those who do bother to vote do so for ritualistic reasons, mainly because they view America as a religion. In the same vein, they go to church every Sunday and say their prayers. The essence of every religion is the ritualistic re-enactment of the sacred myth or cannon - which usually takes the form of reciting "sacred" formulas or veneration of "sacred" objects. But the absolutely essential feature of these rituals is their hierophanic nature - that is - a clearly ostensible manifestation of the canon or sacred form.
Any deviation from that canon is blasphemous - if one sacrifices a chicken instead of a lamb, if a sermon sounds like a presentation at the American Sociological Association, if a priest does not wear a prescribed garb, etc, etc, the improper physical form of the ritual violates the principle of hierophanic representation and its is viewed as such by the believers.
In the same vein, if the candidate does not look "presidential" as prescribed by the American civil religion - he violates the hierophanic principle and will be likely rejected by most voters. This is why Nixon lost to Kennedy, why Carter lost to Reagan, why Dukakis lost to Bush, why Bush Sr. lost to Clinton, why Gore lost to Bush Jr, and - or perhaps above all - why Davis lost to Schwarzenegger - the loosing candidates looked more shabby (Nixon), effeminate (Carter), foreign (Dukakis), less "folksy" (Bush Sr., Gore) , or simply was not a movie star (Davis).
With Bush Jr and Kerry it is hard to tell - Bush Jr. certainly looks more "folksy" in a redneck way (which is why most of the urban voters hate him) - but he also increasingly looks more like a figure-head rather than a leader, Cheney and Rumsfeld really running the show.
Wojtek