I believe one of the reasons why so many people are attracted to the concept of President Barack Obama is because of a sour taste from the quasi-hereditary feeling generated from President George Bush (the Second). It's obvious that there were tens of thousands of people more qualified, more intelligent and better leaders than President Bush available to serve as a Republican President, but because he was born the son of a President, George Bush beat out everyone else. That's disheartening.
Barack Obama, by contract, earned everything he's got. His father had government connections -- in Kenya. That didn't help Barack. He's wickedly intelligent and has performed well under pressure, as well as caught a ton of political lucky breaks, to become a viable pre-announcement presidential candidate. That's a heartwarming story as it cuts to the center of what's best about the United States: we believe in upward mobility and meritocracy, where anyone born poor can become wealthy and class doesn't exist. Now, that isn't objectively true (the best determinant of whether a particular American will earn above-average or below-average income is whether his or her parents earned above-average or below-average income) but because most of us want that to be true, we're willing to support taxes and spending that will help make that more true (like cheap or free higher education or cheap loans to small businesses or a progressive income tax where people who earn more money pay more money).
I think we're all generally more willing to support meritocracy taxes and spending when someone who struggled to make it to a position of power, like Bill Clinton or Barack Obama, can speak on its behalf. When very wealthy people advocate for meritocracy taxes, like John Kerry, it sounds a little arrogant and infused with a spirit of noblesse oblige. People who have been broke, as Barack Obama spent most of his life, can connect with voters about why it's smart to raise taxes on what Paris Hilton will inherit from her family and use that money to buy health insurance for everyone or college scholarships or hiring more teachers or police officers. I think John Edwards can also speak with authenticity on the topic, especially because he's made the eradication of poverty - the grinding, Third World poverty persisting too long -- central to his campaign. I don't know if Hilary Clinton can speak as compellingly, not because she was born priviliged, but because she only has her opportunity to run because of her husband. Perhaps that's unfair, but I think that's the perception of a former First Lady.