My background is in political philosophy. Over this election season found it interesting that one could break down the three most promenient candidates roughly into the three competing ideologies of the left over the past 50-60 years.
Edwards would obviously represent the old economic left which has made up such an important part of the Democratic coalition since the time of William Jennings Bryant. Because the left was globally so deeply influence by Marxism, this was the most radical wing of the party through the Depression era. U.S. labor history is unusually violent. The Depression was perhaps the only time America has come close to outright revolution.
In most Western countries, the economic left was broadly sympathetic to Marxism and, after the Russian revolution, to Leninism. The centrist wing of the Democratic party has mostly challenged the left through the twentith century. These were progressive liberals who believed the system was worth saving and sought to do so via technocratic means. They created social programs called the New Deal to avert the threat from Communism and the true potential for revolution during the thirties. This wing, I would argue, is what Bill and Hillary Clinton represent.
In the 50's and especially in the 60's, the New Left emerged. While liberal progressives persecuted the old left via anti-communism, the New Left challenged the national security concensus that was being forged by the centrist left and right in its attack on Communism. The New Left was not Communist--at least not Marxist or Leninist--so much as it was anti-anti-communist. What the New Left challenged was the world that was being created by the commercialized and beauracratized society growing in the US. They were broadly sympathetic to the old left economic critique, but they sought to go beyond the analysis of social oppression not only in terms of economic empowerment, but also in attempting to understand how society created relations of oppression in multiple ways such as in gender, race, and culture. There were deep questions asked about the existential status of the human agent, and a conclusion reached that the economically derived ideal of "american dream" was a chimera that could never resolve our existential needs.
From here, of course, we all know what happened. The Cold War, white backlash at civil rights successes, Vietnam, and the deep skepticism of American justice both at home and abroad the animated the New Left left it vulnerable to the attack of the New Right. As it happened, the New Right found an extraordinary spokesman in Ronald Reagan. He articulated the values of conservatism in a way that the people found enormously persuasive and attractive. Republicans learned through Reagan how to appeal to people's hearts, and not just to their heads.
In the 90's, the left thought they had found a similar spokesman in the Bill Clinton. The only problem was that, ultimately, he never really was bought into those values. In the first place he was much more a centrist technocratic progressive than any sort of New Leftist. Obviously, he found broad sympathy with the groups who supported those values, but in the end, there never seemed to be firm a grounding of New Leftist ideology to guide him and he ended up as perhaps slightly to left of Eisenhower when all was said and done.
You probably understand by this point that I am claiming the Barack Obama is the candidate that represents the values of the New Left. The New Left sought a participatory ethic to its politics which challenged the beauracratized politics of the National Security state. It saw politics as more that lending consent to competing governmental centers of power and policy, but rather as what individuals engaged in when they contested among themselves the nature of the good life and the just society. It challenged the notion that existential value could ever be resolved in a private choices, and argued that it was worth engaging in and pursue them among our fellow citizens. That the environment was not a resource to be used or conserved, the ground on which the deepest values and roots of our cultures grew, and thus must be preserved in its own inherently natural possibilities. It believed that reasoned political discussion was the essence democratic politics--that persuasion forged a bound among those who were willing to engage it.
Obama, I would argue, is the candidate who at least implicitly--and in many cases overtly--understands the these values. They are deeply interwoven into his rhetoric. When he argues for an existential value like "hope" and asked us to pursue a "new politics", he is asking us to embrace the ethics of the New Left. Obama, in a way Bill Clinton never even seemed to consider, has embraced the ideals of the New Left. This is why he truly could be the Democratic Reagan.