Obama was made famous when he delivered the 2004 Democratic National Convention keynote address. It gave him a chance to show people his speaking abilities and the like. People got really excited about him.
People like him because he talks at length about the bullshit of modern American politics, but carries a hopeful tone AFAIK. He is outwardly moderate, and thus electable, which is good for the Democrats because, well, Hillary Clinton isn't.
I live in Chicago, he has done next to nothing as far as I can tell, and people love him.
Obama would have had more influence in Chicago two years ago. Your representative in the US Senate does not deal with state matters, but with national matters and national legislature. That being said, he couldn't do much with a Republican majority.
Anyway, he has made some good publicity moves and has managed to extend the political capital he gained at the 2004 convention. Most people don't know what he's done... but know who he is and like him. That's whats really important. Look at Bush.
