He has demonstrated a profound ability to inspire people and to win over skeptics. In order to be successful, he will have to use these abilities to bring a substantial majority of the population along with him in a consensus for a change in the way we see the relationship between the individual and society, the obligations of each to the other, and a new understanding of the realities of the world and of the place of the USA in the world.
Jimmy Carter demonstrated that you cannot just tell the US electorate that our situation has changed and we must adapt to it. Unless the President can make a majority see and accept the facts of the case, he will be simply out bid by the next big lier and denier who comes along. It would be foolish to rule out the possibility of the emergence of a new leader in the mold of Ronald Reagan by 2012 or 2016. The population must be vaccinated against such a catastrophic possibility. The best way to accomplish that is by leading a transformation of the country into a better and more successful society. Accomplishing that would be Obama's greatest legacy. Anything less just sets us up for the next leadership disaster. As the Dutch said while fighting the Spanish: "It is not necessary to have hope in order to persevere."
See How Obama won for an interesting take on Obama's organisation and ego. Of course he will eventually be found to have feet of clay, like everyone else. But it is the manner of doing politics, of building society, of engaging people's hopes and dreams which can endure. notes from no w here
A couple of years as President will screw him up anyway: I don't believe it's possible to stay grounded in reality to the end of the first term, never mind the second term.
Perhaps stuff like abortion, gays, and assualt weapons in private hands will finanaly be taken off the table and cease to exist as mainstream political issues - or wedge issues used to contra-distinguish major Presidential candidates and parties. Perhaps the issue will become not regulation/deregulation, but what kind of regulation. Perhaps the notion of invading a country because you don't like it's regime will come to be seen as absurd.
We can live in hope, but we must also watch and see whether real change is intended. notes from no w here