Chicago Mayor more powerful.......

I've heard alot in my life that the Mayor of Chicago is more powerful then the president, (Not just the Daleys but any Mayor of Chicago) most noteably by my father whom is a life-long Chicagoan, but I was reading an article on Senator Obama and he proposed this idea as well and it got me thinking if such an obsurd statement might actually hold water. Now that I'm thinking about it, I remember hearing it on a couple different Chicago based documentaries. I just want to know what you guys think about it and (or) any instances where you think these statements might have originated. I'm interested to know why people would say that, personally, I don't understand it and nobody has gone in to the hows and whys of it.>