One will be hard put to find a defining reason for the successful candidacy run of President-elect B. Obama that will subsume all other reasons: economic panic is the reason Charles Krauthammer gives; Pat Buchanan seconds this and adds the Republicans' inability to alter the perception that we are losing the America that we grew up in.
Let me add a voice, silenced now eighteen years (1990), that of one of my greatest mentors, Walker Percy. Percy, author and medical doctor, turned his forensic eye to the entity most troubling to modern persons and, therefore, the most disputed; namely, the self. A self-taught student of the Existentialists, Percy performed autopsies on the so-called autonomous self with acumen, writhing humor, and piercing insight in both his fiction and non-fiction. My favorite non-fiction book in his opus is Lost in the Cosmos, with Message in the Bottle a close second; neither has lost its timeless wisdom today.
Michael A. Mikolajczak, in a tidy essay on Percy's book cites a quotation by Christopher Lasch which, in my opinion, gives an essential reason for president-elect Obama's victory:
The contemporary climate is therapeutic, not religious. People today hunger not for personal salvation, let alone for the restoration of an earlier golden age, but for the feeling, that momentary illusion, of personal well-being, health, and psychic security. Even the radicalism of the sixties served, for many of those who embraced it, personal rather than political reasons, not as a substitute religion but as a form of therapy. Radical politics filled empty lives, provided a sense of meaning and purpose.
The jejune logic of this ethic is that if people can "relate to themselves," are "self-fulfilled," become "self-actualized," and "get in touch with their feelings," they will, perforce, be happy, kind, and loving. Deriving largely from Rousseau, this ethic rests on a whimsey that human beings are flower buds which, if only allowed to blossom, will delight all beholders and freshen all nostrils. But as Allan Bloom points out, Woody Allen has basically made his film career exploiting the foolishness of this ethic.